:root,
[data-theme="dark"] {
    /* Dracula — restored */
    --bg-primary: #282a36;
    --bg-secondary: #21222c;
    --bg-card: #343746;
    --text-primary: #f8f8f2;
    --text-secondary: #bdbecf;
    --accent: #bd93f9;
    --accent-hover: #cfa5ff;
    --accent-deep: #8458d4;
    --accent-bg: rgba(189, 147, 249, 0.22);
    --accent-bg-subtle: rgba(189, 147, 249, 0.12);
    --accent-glow: rgba(189, 147, 249, 0.50);
    --accent-soft: rgba(189, 147, 249, 0.18);
    --success: #50fa7b;
    --danger: #ff5555;
    --warning: #f1fa8c;
    --border: #44475a;
    --border-strong: rgba(189, 147, 249, 0.45);
    --code-bg: #21222c;
    --code-text: #f8f8f2;
    --code-keyword: #8be9fd;
    --sidebar-bg: rgba(33, 34, 44, 0.85);
    --sidebar-header-bg: rgba(25, 26, 33, 0.85);
    --hover-bg: rgba(255, 255, 255, 0.05);
    --hover-bg-strong: rgba(255, 255, 255, 0.10);
    --shadow: rgba(0, 0, 0, 0.50);
    --font-mono: 'Cascadia Code', 'Fira Code', 'JetBrains Mono', 'Consolas', monospace;

    /* Cool metal — graphite/steel */
    --metal-1: #2c2f3d;
    --metal-2: #3d4254;
    --metal-3: #565d72;
    --metal-light-1: #b8bcd0;
    --metal-light-2: #d8dce8;
    --metal-edge: rgba(216, 220, 232, 0.18);

    /* Composite gradients */
    --header-bg: linear-gradient(180deg, rgba(33, 34, 44, 0.72), rgba(20, 21, 28, 0.85));
    --card-bg: linear-gradient(160deg, rgba(52, 55, 70, 0.92), rgba(33, 34, 44, 0.96));
    --title-gradient: linear-gradient(135deg, #ffffff 0%, #cfa5ff 50%, #bd93f9 100%);
    --accent-brushed: linear-gradient(180deg, #d6b8ff 0%, #bd93f9 35%, #8458d4 100%);
    --accent-brushed-hover: linear-gradient(180deg, #e2c5ff 0%, #c8a4ff 35%, #9568e0 100%);
    --section-card-shadow: 0 12px 36px rgba(0, 0, 0, 0.55), 0 0 24px rgba(189, 147, 249, 0.10);
}

[data-theme="light"] {
    /* IntelliJ Light — restored */
    --bg-primary: #f4f6fa;
    --bg-secondary: #e8ecf3;
    --bg-card: #ffffff;
    --text-primary: #080808;
    --text-secondary: #6c707e;
    --accent: #3574f0;
    --accent-hover: #2b67d1;
    --accent-deep: #1f5bbd;
    --accent-bg: rgba(53, 116, 240, 0.14);
    --accent-bg-subtle: rgba(53, 116, 240, 0.07);
    --accent-glow: rgba(53, 116, 240, 0.38);
    --accent-soft: rgba(53, 116, 240, 0.14);
    --success: #208a3c;
    --danger: #c94f4f;
    --warning: #a1871f;
    --border: rgba(53, 116, 240, 0.20);
    --border-strong: rgba(53, 116, 240, 0.45);
    --code-bg: #f7f8fa;
    --code-text: #080808;
    --code-keyword: #3574f0;
    --sidebar-bg: rgba(247, 248, 250, 0.85);
    --sidebar-header-bg: rgba(232, 236, 243, 0.85);
    --hover-bg: rgba(0, 0, 0, 0.04);
    --hover-bg-strong: rgba(53, 116, 240, 0.10);
    --shadow: rgba(0, 0, 0, 0.12);

    --metal-1: #c5cad6;
    --metal-2: #d4d8e3;
    --metal-3: #e2e6ee;
    --metal-light-1: #5d6470;
    --metal-light-2: #404a58;
    --metal-edge: rgba(40, 50, 70, 0.18);

    --header-bg: linear-gradient(180deg, rgba(255, 255, 255, 0.85), rgba(232, 236, 243, 0.92));
    --card-bg: linear-gradient(160deg, rgba(255, 255, 255, 0.96), rgba(244, 246, 250, 0.92));
    --title-gradient: linear-gradient(135deg, #080808 0%, #1f5bbd 50%, #3574f0 100%);
    --accent-brushed: linear-gradient(180deg, #5a92ff 0%, #3574f0 50%, #1f5bbd 100%);
    --accent-brushed-hover: linear-gradient(180deg, #7ba6ff 0%, #4884ff 50%, #2964c8 100%);
    --section-card-shadow: 0 8px 28px rgba(40, 60, 100, 0.18), 0 0 20px rgba(53, 116, 240, 0.10);
}

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    line-height: 1.6;
    transition: background-color 0.2s, color 0.2s;
}

.container {
    max-width: 1100px;
    margin: 0 auto;
    padding: 20px;
}

/* Header */
.header {
    background-color: var(--bg-secondary);
    border-bottom: 1px solid var(--border);
    padding: 16px 0;
    margin-bottom: 30px;
}

.header h1 {
    font-size: 1.5rem;
    font-weight: 600;
}

.header .subtitle {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

/* Cards */
.card {
    background-color: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 20px;
    margin-bottom: 16px;
    transition: border-color 0.2s;
}

.card:hover {
    border-color: var(--accent);
}

.card h2 {
    font-size: 1.1rem;
    margin-bottom: 8px;
}

.card .meta {
    color: var(--text-secondary);
    font-size: 0.85rem;
    margin-bottom: 12px;
}

/* Badges */
.badge {
    display: inline-block;
    padding: 2px 10px;
    border-radius: 12px;
    font-size: 0.75rem;
    font-weight: 600;
    text-transform: uppercase;
}

.badge-beginner { background-color: #1b5e20; color: #a5d6a7; }
.badge-intermediate { background-color: #e65100; color: #ffcc80; }
.badge-advanced { background-color: #b71c1c; color: #ef9a9a; }
.badge-completed { background-color: var(--success); color: #282a36; }
.badge-given-up { background-color: var(--danger); color: #ffffff; }

[data-theme="light"] .badge-beginner { background-color: #d4edda; color: #155724; }
[data-theme="light"] .badge-intermediate { background-color: #fff3cd; color: #856404; }
[data-theme="light"] .badge-advanced { background-color: #f8d7da; color: #721c24; }
[data-theme="light"] .badge-completed { color: #ffffff; }

/* Category */
.category-header {
    font-size: 1.2rem;
    color: var(--accent);
    margin: 24px 0 12px;
    padding-bottom: 8px;
    border-bottom: 1px solid var(--border);
}

/* Code Editor */
.code-editor {
    width: 100%;
    min-height: 300px;
    background-color: var(--code-bg);
    color: var(--code-text);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 16px;
    font-family: var(--font-mono);
    font-size: 14px;
    line-height: 1.5;
    tab-size: 4;
    resize: vertical;
}

.code-editor:focus {
    outline: none;
    border-color: var(--accent);
}

/* Buttons */
.btn {
    display: inline-block;
    padding: 8px 20px;
    border: none;
    border-radius: 6px;
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: background-color 0.2s;
    text-decoration: none;
}

.btn-primary {
    background-color: var(--accent);
    color: white;
}

.btn-primary:hover {
    background-color: var(--accent-hover);
}

.btn-secondary {
    background-color: transparent;
    color: var(--text-secondary);
    border: 1px solid var(--border);
}

.btn-secondary:hover {
    border-color: var(--text-secondary);
    color: var(--text-primary);
}

.btn-danger {
    background-color: var(--danger);
    color: white;
    border: none;
}

.btn-danger:hover {
    filter: brightness(1.1);
}

.btn-group {
    display: flex;
    gap: 10px;
    margin-top: 16px;
}

/* Result */
.result-box {
    border-radius: 6px;
    padding: 16px;
    margin-top: 16px;
}

.result-success {
    background-color: rgba(40, 167, 69, 0.15);
    border: 1px solid var(--success);
}

.result-failure {
    background-color: rgba(220, 53, 69, 0.15);
    border: 1px solid var(--danger);
}

.result-box h3 {
    margin-bottom: 8px;
}

.result-box pre {
    font-family: var(--font-mono);
    font-size: 0.85rem;
    white-space: pre-wrap;
    color: var(--text-secondary);
}

/* Concepts */
.concepts-section {
    margin-top: 24px;
}

.concept-card {
    background-color: var(--accent-bg-subtle);
    border: 1px solid var(--accent);
    border-radius: 8px;
    padding: 16px;
    margin-bottom: 12px;
}

.concept-card h3 {
    color: var(--accent);
    font-size: 1rem;
    margin-bottom: 8px;
}

.concept-card p,
.concept-text {
    color: var(--text-secondary);
    font-size: 0.9rem;
    line-height: 1.6;
}

.concept-code {
    display: block;
    background-color: var(--code-bg);
    border: 1px solid var(--border);
    border-radius: 6px;
    padding: 12px 16px;
    margin: 10px 0;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    line-height: 1.5;
    overflow-x: auto;
    color: var(--code-text);
}

.concept-code code {
    font-family: inherit;
    background: none;
    padding: 0;
    border: none;
    color: inherit;
}

.concept-inline-code {
    background-color: var(--code-bg);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 1px 6px;
    font-family: var(--font-mono);
    font-size: 0.85em;
    color: var(--code-keyword);
}

/* Progress */
.progress-bar {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 20px;
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.progress-fill {
    flex: 1;
    height: 6px;
    background-color: var(--border);
    border-radius: 3px;
    overflow: hidden;
}

.progress-fill-inner {
    height: 100%;
    background-color: var(--accent);
    border-radius: 3px;
    transition: width 0.3s;
}

.progress-fill-split {
    display: flex;
    width: 100%;
    height: 100%;
}

.progress-fill-solved {
    background-color: var(--success);
    height: 100%;
    transition: width 0.3s;
}

.progress-fill-givenup {
    background-color: var(--danger);
    height: 100%;
    transition: width 0.3s;
}

.progress-counters {
    display: flex;
    gap: 12px;
    align-items: center;
}

.progress-counter-solved {
    color: var(--success);
    font-weight: 600;
}

.progress-counter-givenup {
    color: var(--danger);
    font-weight: 600;
}

/* Challenge description */
.challenge-description {
    background-color: var(--bg-secondary);
    border-left: 3px solid var(--accent);
    padding: 12px 16px;
    margin-bottom: 16px;
    border-radius: 0 6px 6px 0;
}

/* Breadcrumb */
.breadcrumb {
    margin-bottom: 20px;
    font-size: 0.9rem;
}

.breadcrumb-link {
    color: var(--accent);
    text-decoration: none;
    cursor: pointer;
    background: none;
    border: none;
    font-size: 0.9rem;
    padding: 0;
    font-family: inherit;
}

.breadcrumb-link:hover {
    color: var(--accent-hover);
    text-decoration: underline;
}

.breadcrumb-sep {
    color: var(--text-secondary);
    margin: 0 8px;
}

.breadcrumb-current {
    color: var(--text-primary);
    font-weight: 500;
}

.breadcrumb-counter {
    color: var(--text-secondary);
    margin-left: 8px;
    font-size: 0.85rem;
}

/* Links */
a.challenge-link {
    color: var(--text-primary);
    text-decoration: none;
    display: block;
}

/* IDE-style Sidebar */
.app-layout {
    display: flex;
    min-height: 100vh;
    align-items: stretch;
}

.app-main {
    flex: 1;
    min-width: 0;
}

.sidebar {
    width: 280px;
    flex-shrink: 0;
    background-color: var(--sidebar-bg);
    border-right: 1px solid var(--border);
    display: flex;
    flex-direction: column;
    transition: width 0.2s ease, background-color 0.2s;
    overflow: hidden;
}

.sidebar.collapsed {
    width: 44px;
}

.sidebar-header {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 12px;
    border-bottom: 1px solid var(--border);
    background-color: var(--sidebar-header-bg);
    min-height: 44px;
}

.sidebar-toggle {
    background: transparent;
    border: none;
    color: var(--text-secondary);
    cursor: pointer;
    padding: 4px;
    border-radius: 4px;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
}

.sidebar-toggle:hover {
    background-color: var(--hover-bg-strong);
    color: var(--text-primary);
}

.sidebar-title {
    font-size: 0.72rem;
    font-weight: 600;
    letter-spacing: 1px;
    color: var(--text-secondary);
    text-transform: uppercase;
    white-space: nowrap;
    opacity: 1;
    transition: opacity 0.15s;
}

.sidebar.collapsed .sidebar-title,
.sidebar.collapsed .sidebar-tree {
    opacity: 0;
    pointer-events: none;
}

.sidebar-tree {
    flex: 1;
    overflow-y: auto;
    padding: 8px 0;
    font-size: 0.85rem;
}

.tree-category {
    margin-bottom: 2px;
}

.tree-category-header {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 4px 12px;
    cursor: pointer;
    color: var(--text-primary);
    font-weight: 500;
    user-select: none;
    white-space: nowrap;
}

.tree-category-header:hover {
    background-color: var(--hover-bg);
}

.tree-chevron {
    display: inline-block;
    color: var(--text-secondary);
    font-size: 0.75rem;
    width: 12px;
    transition: transform 0.15s;
    transform: rotate(-90deg);
}

.tree-category.expanded .tree-chevron {
    transform: rotate(0deg);
}

.tree-category-name {
    font-size: 0.85rem;
}

.tree-category-children {
    display: none;
    padding-left: 8px;
}

.tree-category.expanded .tree-category-children {
    display: block;
}

.tree-challenge {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 4px 12px 4px 28px;
    color: var(--text-secondary);
    text-decoration: none;
    cursor: pointer;
    border: none;
    background: none;
    font-family: inherit;
    font-size: 0.85rem;
    width: 100%;
    text-align: left;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
}

.tree-challenge:hover {
    background-color: var(--hover-bg);
    color: var(--text-primary);
}

.tree-challenge-active {
    background-color: var(--accent-bg);
    color: var(--text-primary);
    border-left: 2px solid var(--accent);
    padding-left: 26px;
}

.tree-challenge-active:hover {
    background-color: var(--accent-bg);
    filter: brightness(1.1);
}

.tree-file-icon {
    color: var(--code-keyword);
    font-size: 0.8rem;
    flex-shrink: 0;
}

.tree-challenge-title {
    overflow: hidden;
    text-overflow: ellipsis;
    flex: 1;
}

.tree-check {
    color: var(--success);
    font-size: 0.85rem;
    flex-shrink: 0;
}

.tree-cross {
    color: var(--danger);
    font-size: 0.95rem;
    font-weight: 700;
    flex-shrink: 0;
}

/* Category numbering */
.category-number {
    display: inline-block;
    min-width: 1.6rem;
    height: 1.6rem;
    line-height: 1.6rem;
    text-align: center;
    background-color: var(--accent-bg-subtle);
    color: var(--accent);
    border-radius: 50%;
    font-size: 0.85rem;
    font-weight: 700;
    margin-right: 8px;
}

/* Header row (title + theme toggle) */
.header-row {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 16px;
}

.header-titles {
    min-width: 0;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 10px;
    flex-shrink: 0;
}

/* Theme Toggle Switch */
.theme-toggle {
    position: relative;
    width: 54px;
    height: 26px;
    background-color: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 13px;
    cursor: pointer;
    padding: 0;
    flex-shrink: 0;
    transition: background-color 0.2s, border-color 0.2s;
}

.theme-toggle:hover {
    border-color: var(--accent);
}

.theme-toggle::before,
.theme-toggle::after {
    position: absolute;
    top: 50%;
    transform: translateY(-50%);
    font-size: 11px;
    color: var(--text-secondary);
    pointer-events: none;
    line-height: 1;
}

.theme-toggle::before {
    content: "\263D";
    left: 7px;
}

.theme-toggle::after {
    content: "\2600";
    right: 7px;
}

.theme-toggle-thumb {
    position: absolute;
    top: 2px;
    left: 2px;
    width: 20px;
    height: 20px;
    background-color: var(--accent);
    border-radius: 50%;
    transition: transform 0.25s cubic-bezier(0.4, 0, 0.2, 1), background-color 0.2s;
    box-shadow: 0 1px 3px var(--shadow);
}

[data-theme="light"] .theme-toggle-thumb {
    transform: translateX(26px);
}

@media (max-width: 768px) {
    .sidebar {
        width: 44px;
    }
    .sidebar:not(.collapsed) {
        position: fixed;
        z-index: 100;
        height: 100vh;
        width: 260px;
        box-shadow: 4px 0 12px var(--shadow);
    }
}

/* Section Summary Modal */
.modal-overlay {
    position: fixed;
    inset: 0;
    background-color: rgba(0, 0, 0, 0.55);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    padding: 20px;
}

.modal-box {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 24px 28px;
    max-width: 520px;
    width: 100%;
    box-shadow: 0 10px 30px var(--shadow);
}

.modal-title {
    margin-top: 0;
    margin-bottom: 8px;
}

.modal-subtitle {
    color: var(--text-secondary);
    margin-bottom: 16px;
}

.modal-stats {
    display: flex;
    gap: 18px;
    margin-bottom: 16px;
    font-size: 0.95rem;
}

.modal-stat-solved {
    color: var(--success);
    font-weight: 600;
}

.modal-stat-givenup {
    color: var(--danger);
    font-weight: 600;
}

.modal-review {
    margin-top: 12px;
    padding-top: 12px;
    border-top: 1px solid var(--border);
}

.modal-review h4 {
    margin: 0 0 8px 0;
    color: var(--danger);
}

.modal-review ul {
    margin: 0;
    padding-left: 20px;
}

.modal-actions {
    margin-top: 18px;
    display: flex;
    justify-content: flex-end;
    gap: 10px;
}

/* Bonus page */
.category-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    flex-wrap: wrap;
}

.category-bonus-form {
    margin: 0;
}

.btn-bonus {
    background-color: transparent;
    color: var(--accent);
    border: 1px solid var(--accent);
    font-weight: 600;
}

.btn-bonus:hover {
    background-color: var(--accent-bg-subtle);
}

.tree-bonus {
    font-weight: 600;
    color: var(--accent);
}

.tree-bonus-icon {
    font-size: 0.95rem;
    flex-shrink: 0;
    margin-right: 2px;
}

.bonus-intro {
    background-color: var(--bg-secondary);
    border-left: 3px solid var(--accent);
    padding: 12px 16px;
    margin-bottom: 16px;
    border-radius: 0 6px 6px 0;
    color: var(--text-secondary);
}

.bonus-legend {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin-bottom: 18px;
}

.bonus-legend-item {
    padding: 4px 10px;
    border-radius: 4px;
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.5px;
    text-transform: uppercase;
}

.bonus-type-filter {
    display: flex;
    gap: 10px;
    flex-wrap: wrap;
    margin-bottom: 22px;
    padding-bottom: 14px;
    border-bottom: 1px solid var(--border);
}

.bonus-pill {
    background: var(--bg-secondary);
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: 999px;
    padding: 8px 18px;
    font-size: 0.85rem;
    font-weight: 600;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    cursor: pointer;
    transition: all 0.15s ease;
}

.bonus-pill:hover {
    transform: translateY(-1px);
    filter: brightness(1.08);
}

.bonus-pill.active {
    color: #ffffff;
    border-color: transparent;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.25);
}

.bonus-pill.bonus-type-trap.active { background-color: #f1c40f; color: #3a2e00; }
.bonus-pill.bonus-type-rule.active { background-color: #3498db; }
.bonus-pill.bonus-type-gotcha.active { background-color: var(--danger); }
.bonus-pill.bonus-type-tip.active { background-color: var(--success); color: #0d2a14; }

.bonus-stack {
    display: flex;
    flex-direction: column;
    gap: 16px;
    max-width: 860px;
    margin: 0 auto;
}

.bonus-empty-type {
    max-width: 860px;
    margin: 24px auto 0;
    padding: 24px;
    text-align: center;
    color: var(--text-secondary);
    background-color: var(--bg-secondary);
    border: 1px dashed var(--border);
    border-radius: 8px;
    display: none;
}

.bonus-card.hidden,
.bonus-quiz.hidden,
.bonus-legend.hidden {
    display: none !important;
}

.bonus-card {
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 20px 24px;
    border-left-width: 6px;
    border-left-style: solid;
    font-size: 1rem;
}

.bonus-card-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 10px;
}

.bonus-card-badge {
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    padding: 3px 8px;
    border-radius: 4px;
    flex-shrink: 0;
}

.bonus-card-title {
    margin: 0;
    font-size: 1.2rem;
    line-height: 1.3;
}

.bonus-card-body {
    color: var(--text-secondary);
    font-size: 1rem;
    line-height: 1.6;
}

.bonus-card-body code.concept-inline-code {
    font-size: 0.85em;
}

/* Card type colors */
.bonus-type-trap {
    border-left-color: #f1c40f;
    background-color: color-mix(in srgb, #f1c40f 8%, var(--bg-secondary));
}
.bonus-type-trap .bonus-card-badge,
.bonus-legend-item.bonus-type-trap {
    background-color: #f1c40f;
    color: #3a2e00;
}

.bonus-type-rule {
    border-left-color: #3498db;
    background-color: color-mix(in srgb, #3498db 8%, var(--bg-secondary));
}
.bonus-type-rule .bonus-card-badge,
.bonus-legend-item.bonus-type-rule {
    background-color: #3498db;
    color: #ffffff;
}

.bonus-type-gotcha {
    border-left-color: var(--danger);
    background-color: color-mix(in srgb, var(--danger) 8%, var(--bg-secondary));
}
.bonus-type-gotcha .bonus-card-badge,
.bonus-legend-item.bonus-type-gotcha {
    background-color: var(--danger);
    color: #ffffff;
}

.bonus-type-tip {
    border-left-color: var(--success);
    background-color: color-mix(in srgb, var(--success) 8%, var(--bg-secondary));
}
.bonus-type-tip .bonus-card-badge,
.bonus-legend-item.bonus-type-tip {
    background-color: var(--success);
    color: #0d2a14;
}

/* Flip quiz card */
.bonus-quiz {
    perspective: 1800px;
}

.bonus-quiz .flip-inner {
    display: grid;
    width: 100%;
    transform-style: preserve-3d;
    transition: transform 0.7s cubic-bezier(0.2, 0.8, 0.2, 1);
}

.bonus-quiz.flipped .flip-inner {
    transform: rotateY(180deg);
}

.bonus-quiz .flip-front,
.bonus-quiz .flip-back {
    grid-area: 1 / 1;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 24px 26px;
    border-left-width: 6px;
    border-left-style: solid;
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.bonus-quiz .flip-front {
    min-height: 220px;
}

.bonus-quiz.bonus-type-trap .flip-front,
.bonus-quiz.bonus-type-trap .flip-back { border-left-color: #f1c40f; background-color: color-mix(in srgb, #f1c40f 10%, var(--bg-secondary)); }
.bonus-quiz.bonus-type-rule .flip-front,
.bonus-quiz.bonus-type-rule .flip-back { border-left-color: #3498db; background-color: color-mix(in srgb, #3498db 10%, var(--bg-secondary)); }
.bonus-quiz.bonus-type-gotcha .flip-front,
.bonus-quiz.bonus-type-gotcha .flip-back { border-left-color: var(--danger); background-color: color-mix(in srgb, var(--danger) 10%, var(--bg-secondary)); }
.bonus-quiz.bonus-type-tip .flip-front,
.bonus-quiz.bonus-type-tip .flip-back { border-left-color: var(--success); background-color: color-mix(in srgb, var(--success) 10%, var(--bg-secondary)); }

.bonus-quiz .flip-front .bonus-card-badge,
.bonus-quiz .flip-back .bonus-card-badge { align-self: flex-start; }

.bonus-quiz.bonus-type-trap .flip-front .bonus-card-badge,
.bonus-quiz.bonus-type-trap .flip-back .bonus-card-badge { background-color: #f1c40f; color: #3a2e00; }
.bonus-quiz.bonus-type-rule .flip-front .bonus-card-badge,
.bonus-quiz.bonus-type-rule .flip-back .bonus-card-badge { background-color: #3498db; color: #ffffff; }
.bonus-quiz.bonus-type-gotcha .flip-front .bonus-card-badge,
.bonus-quiz.bonus-type-gotcha .flip-back .bonus-card-badge { background-color: var(--danger); color: #ffffff; }
.bonus-quiz.bonus-type-tip .flip-front .bonus-card-badge,
.bonus-quiz.bonus-type-tip .flip-back .bonus-card-badge { background-color: var(--success); color: #0d2a14; }

.bonus-quiz .flip-back {
    transform: rotateY(180deg);
}

.flip-cta-title {
    margin: 0;
    font-size: 1.35rem;
    line-height: 1.3;
}

.flip-cta-title em {
    text-transform: uppercase;
    font-style: normal;
    letter-spacing: 0.5px;
}

.flip-cta-text {
    color: var(--text-secondary);
    margin: 0;
    font-size: 1rem;
    line-height: 1.5;
}

.flip-front .btn {
    align-self: flex-start;
}

.quiz-question {
    font-size: 1rem;
    line-height: 1.55;
    color: var(--text-primary);
}

.quiz-question pre.concept-code {
    margin: 10px 0;
}

.quiz-options {
    list-style: none;
    padding: 0;
    margin: 0;
    display: flex;
    flex-direction: column;
    gap: 8px;
    counter-reset: quiz-opt;
}

.quiz-option {
    padding: 12px 14px 12px 48px;
    background-color: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 6px;
    cursor: pointer;
    position: relative;
    font-size: 0.95rem;
    line-height: 1.5;
    transition: background-color 0.12s ease, border-color 0.12s ease;
    counter-increment: quiz-opt;
}

.quiz-option::before {
    content: counter(quiz-opt, upper-alpha);
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    width: 26px;
    height: 26px;
    border-radius: 50%;
    background-color: var(--bg-secondary);
    border: 1px solid var(--border);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 0.8rem;
    color: var(--text-secondary);
}

.quiz-option:hover {
    border-color: var(--accent);
    background-color: color-mix(in srgb, var(--accent) 6%, var(--bg-primary));
}

.quiz-option.selected {
    border-color: var(--accent);
    background-color: color-mix(in srgb, var(--accent) 14%, var(--bg-primary));
}

.quiz-option.selected::before {
    background-color: var(--accent);
    color: #ffffff;
    border-color: var(--accent);
}

.quiz-options.revealed .quiz-option {
    cursor: default;
}

.quiz-options.revealed .quiz-option[data-correct="true"] {
    border-color: var(--success);
    background-color: color-mix(in srgb, var(--success) 18%, var(--bg-primary));
}

.quiz-options.revealed .quiz-option[data-correct="true"]::before {
    content: "\2713";
    background-color: var(--success);
    color: #0d2a14;
    border-color: var(--success);
}

.quiz-options.revealed .quiz-option.selected[data-correct="false"] {
    border-color: var(--danger);
    background-color: color-mix(in srgb, var(--danger) 18%, var(--bg-primary));
}

.quiz-options.revealed .quiz-option.selected[data-correct="false"]::before {
    content: "\2717";
    background-color: var(--danger);
    color: #ffffff;
    border-color: var(--danger);
}

.quiz-actions {
    display: flex;
    gap: 10px;
    margin-top: 4px;
}

.quiz-explanation {
    display: none;
    background-color: var(--bg-primary);
    border: 1px solid var(--border);
    border-left: 4px solid var(--accent);
    border-radius: 6px;
    padding: 12px 14px;
    font-size: 0.95rem;
    line-height: 1.55;
    color: var(--text-secondary);
}

.quiz-explanation strong {
    display: block;
    color: var(--text-primary);
    margin-bottom: 6px;
    letter-spacing: 0.5px;
    font-size: 0.8rem;
    text-transform: uppercase;
}

.quiz-explanation-body pre.concept-code {
    margin: 8px 0;
}

.bonus-quiz.flipped .quiz-options.revealed + .quiz-actions + .quiz-explanation,
.quiz-options.revealed ~ .quiz-explanation {
    display: block;
}

/* Solution label above editor */
.solution-label {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 6px;
}

.solution-label-badge {
    background-color: var(--danger);
    color: white;
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 1px;
    padding: 3px 8px;
    border-radius: 4px;
}

.solution-label-text {
    color: var(--text-secondary);
    font-size: 0.9rem;
}

.cm-readonly .CodeMirror {
    border-color: var(--danger);
    opacity: 0.92;
}

/* ============================================================
   TUTORIAL
   ============================================================ */

.tutor-body {
    margin: 0;
    padding: 0;
    min-height: 100vh;
    background:
        radial-gradient(1200px 600px at 15% 10%, color-mix(in srgb, var(--accent) 18%, transparent), transparent 60%),
        radial-gradient(900px 500px at 85% 90%, color-mix(in srgb, var(--success) 14%, transparent), transparent 60%),
        var(--bg-primary);
    color: var(--text-primary);
    overflow-x: hidden;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

.tutor-stage {
    position: relative;
    width: 100%;
    max-width: 1100px;
    margin: 0 auto;
    padding: 50px 24px 240px;
    min-height: 100vh;
    box-sizing: border-box;
}

.tutor-scene {
    display: none;
    animation: sceneEnter 0.6s ease-out;
}

.tutor-scene.active {
    display: block;
}

@keyframes sceneEnter {
    from { opacity: 0; transform: translateY(18px) scale(0.98); }
    to   { opacity: 1; transform: translateY(0) scale(1); }
}

/* --- Scene 1: intro --- */
.scene-intro {
    text-align: center;
    padding: 40px 20px;
}

.scene-intro-art {
    position: relative;
    width: 180px;
    height: 180px;
    margin: 0 auto 24px;
    display: flex;
    align-items: center;
    justify-content: center;
}

.scene-intro-logo {
    font-size: 110px;
    filter: drop-shadow(0 20px 40px rgba(0, 0, 0, 0.4));
    animation: logoBounce 2.4s ease-in-out infinite;
}

@keyframes logoBounce {
    0%, 100% { transform: translateY(0) rotate(-4deg); }
    50%      { transform: translateY(-12px) rotate(4deg); }
}

.scene-intro-spark {
    position: absolute;
    width: 14px;
    height: 14px;
    border-radius: 50%;
    background: radial-gradient(circle, #fff 0%, var(--accent) 55%, transparent 75%);
    top: 20%;
    left: 18%;
    animation: sparkle 2.8s ease-in-out infinite;
    opacity: 0.8;
}

.scene-intro-spark.spark-2 {
    top: 70%; left: 80%;
    width: 10px; height: 10px;
    animation-delay: 0.8s;
    background: radial-gradient(circle, #fff 0%, var(--success) 55%, transparent 75%);
}

.scene-intro-spark.spark-3 {
    top: 25%; left: 82%;
    width: 8px; height: 8px;
    animation-delay: 1.4s;
    background: radial-gradient(circle, #fff 0%, #f1c40f 55%, transparent 75%);
}

@keyframes sparkle {
    0%, 100% { transform: scale(0.6); opacity: 0.2; }
    50%      { transform: scale(1.4); opacity: 1;   }
}

.scene-intro-title {
    font-size: 3rem;
    font-weight: 800;
    letter-spacing: -0.5px;
    margin: 0 0 12px;
    background: linear-gradient(120deg, var(--text-primary), color-mix(in srgb, var(--accent) 70%, var(--text-primary)));
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
    animation: fadeSlideUp 0.8s 0.2s both;
}

.scene-intro-subtitle {
    font-size: 1.2rem;
    color: var(--text-secondary);
    max-width: 640px;
    margin: 0 auto 32px;
    line-height: 1.55;
    animation: fadeSlideUp 0.8s 0.4s both;
}

.scene-intro-badges {
    display: flex;
    gap: 14px;
    justify-content: center;
    flex-wrap: wrap;
    margin-bottom: 24px;
}

.intro-badge {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 999px;
    padding: 10px 18px;
    font-size: 0.95rem;
    color: var(--text-secondary);
    display: inline-flex;
    align-items: center;
    gap: 8px;
    animation: fadeSlideUp 0.8s both;
}

.scene-intro-badges .intro-badge:nth-child(1) { animation-delay: 0.6s; }
.scene-intro-badges .intro-badge:nth-child(2) { animation-delay: 0.8s; }
.scene-intro-badges .intro-badge:nth-child(3) { animation-delay: 1.0s; }

.intro-badge-num {
    font-weight: 800;
    font-size: 1.2rem;
    color: var(--accent);
}

.scene-intro-hint {
    color: var(--text-secondary);
    opacity: 0.75;
    font-size: 0.95rem;
    margin-top: 18px;
    animation: fadeSlideUp 0.8s 1.2s both;
}

@keyframes fadeSlideUp {
    from { opacity: 0; transform: translateY(12px); }
    to   { opacity: 1; transform: translateY(0);    }
}

/* --- Shared mock --- */
.mock-app {
    position: relative;
    background-color: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 12px;
    box-shadow: 0 30px 60px -20px rgba(0, 0, 0, 0.5);
    overflow: hidden;
    padding: 22px;
}

.mock-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding-bottom: 14px;
    border-bottom: 1px solid var(--border);
    margin-bottom: 18px;
}

.mock-h1 {
    font-size: 1.1rem;
    font-weight: 700;
}

.mock-theme-toggle {
    width: 40px;
    height: 22px;
    border-radius: 999px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    position: relative;
}
.mock-theme-toggle::after {
    content: '';
    position: absolute;
    width: 16px; height: 16px;
    border-radius: 50%;
    background: var(--accent);
    top: 2px; left: 2px;
}

.mock-progress {
    background: var(--bg-secondary);
    border-radius: 8px;
    padding: 12px 14px;
    margin-bottom: 18px;
    border: 1px solid var(--border);
}

.mock-progress-counters {
    display: flex;
    gap: 14px;
    justify-content: space-between;
    font-size: 0.85rem;
    margin-bottom: 8px;
}

.mock-counter-solved { color: var(--success); font-weight: 600; }
.mock-counter-givenup { color: var(--danger); font-weight: 600; }

.mock-progress-fill {
    height: 8px;
    background: var(--bg-primary);
    border-radius: 4px;
    overflow: hidden;
    position: relative;
}

.mock-progress-split {
    position: absolute;
    left: 0; top: 0; bottom: 0;
    width: 0%;
    background: linear-gradient(90deg, var(--success) 70%, var(--danger) 70%);
}

.mock-category-row {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 14px;
}
.mock-category-row + .mock-category-row { margin-top: 8px; }

.mock-category {
    display: flex;
    align-items: center;
    gap: 10px;
    font-size: 1.15rem;
    font-weight: 700;
    margin: 0;
    color: var(--text-primary);
}

.mock-cat-num {
    background: var(--accent);
    color: #fff;
    width: 28px;
    height: 28px;
    border-radius: 50%;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 0.85rem;
    font-weight: 700;
}

.mock-btn {
    border: 1px solid var(--border);
    background: var(--bg-secondary);
    color: var(--text-primary);
    padding: 8px 14px;
    border-radius: 6px;
    font-size: 0.88rem;
    font-weight: 600;
    cursor: pointer;
    transition: transform 0.1s ease;
}

.mock-btn-primary {
    background: var(--accent-brushed);
    color: #fff;
    border: 1px solid var(--accent);
    text-shadow: 0 1px 0 rgba(0, 0, 0, 0.25);
    box-shadow:
        inset 0 1px 0 rgba(255,255,255,0.40),
        inset 0 -1px 0 rgba(0,0,0,0.18),
        0 0 12px var(--accent-soft);
}
.mock-btn-danger  { background: var(--danger); color: #fff; border-color: transparent; }
.mock-btn-secondary { background: var(--bg-secondary); }
.mock-btn-bonus {
    background: transparent;
    color: var(--accent);
    border: 1px solid var(--accent);
    font-weight: 600;
}

.mock-disabled { opacity: 0.5; cursor: not-allowed; }

.mock-card-list {
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-bottom: 8px;
}

.mock-challenge {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 12px 16px;
}

.mock-challenge h3 {
    margin: 0 0 8px;
    font-size: 1rem;
}

.mock-challenge p {
    color: var(--text-secondary);
    font-size: 0.85rem;
    line-height: 1.45;
    margin: 6px 0 10px;
}

.mock-meta {
    display: flex;
    gap: 8px;
    align-items: center;
    font-size: 0.78rem;
    color: var(--text-secondary);
}

.mock-badge {
    padding: 2px 8px;
    border-radius: 4px;
    font-weight: 700;
    letter-spacing: 0.5px;
    font-size: 0.7rem;
}

.mock-badge-easy   { background: var(--success); color: #0d2a14; }
.mock-badge-intermediate { background: #f1c40f; color: #3a2e00; }
.mock-badge-advanced   { background: var(--danger); color: #fff; }

/* Cursor + callouts */
.tutor-cursor {
    position: absolute;
    width: 24px;
    height: 24px;
    pointer-events: none;
    z-index: 20;
    filter: drop-shadow(0 4px 6px rgba(0,0,0,0.35));
    opacity: 0;
}

.tutor-cursor::before {
    content: '';
    position: absolute;
    inset: 0;
    background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 24 24' fill='%23ffffff' stroke='%23000' stroke-width='1.5'%3E%3Cpath d='M4 3l7 16 2-7 7-2z'/%3E%3C/svg%3E");
    background-repeat: no-repeat;
    background-size: contain;
}

.tutor-callout {
    position: absolute;
    background: var(--accent);
    color: #fff;
    padding: 8px 12px;
    border-radius: 8px;
    font-size: 0.82rem;
    font-weight: 500;
    line-height: 1.4;
    max-width: 260px;
    box-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.5);
    opacity: 0;
    transform: translateY(6px);
    z-index: 15;
}

.tutor-callout::after {
    content: '';
    position: absolute;
    width: 0; height: 0;
    border: 6px solid transparent;
    border-top-color: var(--accent);
    bottom: -12px;
    left: 20px;
}

/* Scene 2 cursor (positions are JS-driven) */
.scene-browse .cursor-browse {
    top: 0;
    left: 0;
}

.scene-browse.active .mock-progress-split { animation: progressGrow 7.6s 0.4s both; }
@keyframes progressGrow { to { width: 18%; } }

/* Click feedback on the cursor */
.cursor-browse.cursor-clicking {
    animation: cursorClick 0.35s ease-out;
}
@keyframes cursorClick {
    0%   { transform: scale(1); }
    40%  { transform: scale(0.7); }
    100% { transform: scale(1); }
}

/* Ring on the element the cursor clicks */
.browse-target-hit {
    box-shadow: 0 0 0 3px var(--accent), 0 0 0 7px color-mix(in srgb, var(--accent) 35%, transparent) !important;
    border-radius: 8px;
    transition: box-shadow 0.2s ease;
    position: relative;
    z-index: 2;
}

/* Explanatory label near the clicked element */
.cursor-label {
    position: absolute;
    transform: translate(-50%, 0);
    background: var(--accent);
    color: #fff;
    padding: 8px 14px;
    border-radius: 8px;
    font-size: 0.85rem;
    font-weight: 500;
    line-height: 1.4;
    max-width: 280px;
    text-align: center;
    box-shadow: 0 10px 30px -10px rgba(0, 0, 0, 0.55);
    opacity: 0;
    pointer-events: none;
    z-index: 25;
    transition: opacity 0.25s ease, transform 0.25s ease;
}
.cursor-label.visible {
    opacity: 1;
    transform: translate(-50%, -4px);
}
.cursor-label::before {
    content: '';
    position: absolute;
    top: -6px;
    left: var(--arrow-x, 50%);
    transform: translateX(-50%) rotate(45deg);
    width: 12px;
    height: 12px;
    background: var(--accent);
    border-radius: 2px;
}
.cursor-label.cursor-label-above {
    transform: translate(-50%, -100%);
}
.cursor-label.cursor-label-above.visible {
    transform: translate(-50%, calc(-100% - 4px));
}
.cursor-label.cursor-label-above::before {
    top: auto;
    bottom: -6px;
}

/* --- Scene 3: solve --- */
.mock-app-challenge {
    display: grid;
    grid-template-columns: 200px 1fr;
    gap: 0;
    padding: 0;
    min-height: 440px;
}

.mock-sidebar {
    background: var(--bg-secondary);
    border-right: 1px solid var(--border);
    padding: 14px;
    font-size: 0.85rem;
}

.mock-sidebar-header {
    font-size: 0.7rem;
    letter-spacing: 1.5px;
    color: var(--text-secondary);
    font-weight: 700;
    margin-bottom: 12px;
}

.mock-tree-cat-name {
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: 8px;
}

.mock-tree-item {
    display: flex;
    justify-content: space-between;
    padding: 6px 10px;
    border-radius: 4px;
    font-size: 0.82rem;
    color: var(--text-secondary);
    margin-left: 12px;
    margin-bottom: 2px;
}

.mock-tree-active {
    background: color-mix(in srgb, var(--accent) 20%, transparent);
    color: var(--text-primary);
}

.mock-tree-item.bonus-tree-hover {
    outline: 1px solid color-mix(in srgb, var(--text-primary) 45%, transparent);
    outline-offset: -1px;
    transition: outline-color 0.2s ease, background 0.2s ease;
}

.mock-tree-item.bonus-tree-flash {
    animation: bonusTreeFlash 0.4s ease-out;
}

@keyframes bonusTreeFlash {
    0%   { background: color-mix(in srgb, var(--accent) 20%, transparent); box-shadow: none; }
    40%  { background: color-mix(in srgb, var(--accent) 55%, transparent); box-shadow: 0 0 0 2px var(--accent); }
    100% { background: color-mix(in srgb, var(--accent) 20%, transparent); box-shadow: none; }
}

.mock-tree-check { color: var(--success); font-weight: 700; }
.mock-tree-cross { color: var(--danger); font-weight: 700; }
.mock-tree-bonus { color: #f1c40f; }

.mock-challenge-main {
    padding: 22px 26px;
    position: relative;
}

.mock-challenge-title {
    margin: 0 0 6px;
    font-size: 1.3rem;
}

.mock-challenge-desc {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin: 0 0 14px;
}

.mock-challenge-desc code {
    background: var(--bg-secondary);
    padding: 1px 6px;
    border-radius: 3px;
    color: var(--accent);
}

.mock-editor {
    background: #1e1e1e;
    color: #d4d4d4;
    padding: 14px 16px;
    border-radius: 6px;
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 0.88rem;
    line-height: 1.6;
    border: 1px solid var(--border);
    margin-bottom: 12px;
}

[data-theme="light"] .mock-editor { background: #f5f5f5; color: #333; }

.mock-editor-line { white-space: pre; }
.mock-editor .kw  { color: #569cd6; font-weight: 600; }
.mock-editor .str { color: #ce9178; }
[data-theme="light"] .mock-editor .kw { color: #0000ff; }
[data-theme="light"] .mock-editor .str { color: #a31515; }

/* Static code blocks (scene 4 locked, scene 5 cards) */
.mock-code {
    background: #1e1e1e;
    color: #d4d4d4;
    padding: 14px 16px;
    border-radius: 6px;
    font-family: 'Consolas', 'Monaco', monospace;
    font-size: 0.88rem;
    line-height: 1.55;
    border: 1px solid var(--border);
    margin: 10px 0 12px;
    white-space: pre;
    overflow-x: auto;
}
.mock-code.mock-code-sm {
    font-size: 0.8rem;
    padding: 10px 12px;
    line-height: 1.5;
}
[data-theme="light"] .mock-code { background: #f5f5f5; color: #333; }

.mock-code .kw  { color: #569cd6; font-weight: 600; }
.mock-code .str { color: #ce9178; }
.mock-code .num { color: #b5cea8; }
.mock-code .cm  { color: #6a9955; font-style: italic; }
[data-theme="light"] .mock-code .kw  { color: #0000ff; }
[data-theme="light"] .mock-code .str { color: #a31515; }
[data-theme="light"] .mock-code .num { color: #098658; }
[data-theme="light"] .mock-code .cm  { color: #008000; }

.mock-code-locked {
    border-color: var(--danger) !important;
    opacity: 0.92;
}

/* Diff view inside a mock-code block */
.mock-code-diff { line-height: 1.6; }
.mock-code-diff .dim { display: block; opacity: 0.55; }
.mock-code-diff .line-rem {
    display: block;
    background: color-mix(in srgb, var(--danger) 22%, transparent);
    color: #ffb4b4;
    border-left: 3px solid var(--danger);
    padding-left: 6px;
    margin-left: -9px;
}
.mock-code-diff .line-add {
    display: block;
    background: color-mix(in srgb, #2ea043 22%, transparent);
    color: #b6f2c1;
    border-left: 3px solid #2ea043;
    padding-left: 6px;
    margin-left: -9px;
}
[data-theme="light"] .mock-code-diff .line-rem { color: #86181d; }
[data-theme="light"] .mock-code-diff .line-add { color: #0a5e2a; }

.giveup-flip.flipped .mock-code-diff .line-add {
    animation: diffAddPulse 0.6s 0.9s 2 both;
}
.giveup-flip.flipped .mock-code-diff .line-rem {
    animation: diffRemPulse 0.6s 0.9s 2 both;
}
@keyframes diffAddPulse {
    0%   { background: color-mix(in srgb, #2ea043 22%, transparent); }
    50%  { background: color-mix(in srgb, #2ea043 55%, transparent); }
    100% { background: color-mix(in srgb, #2ea043 22%, transparent); }
}

/* Solution reveal on the real challenge page */
.solution-diff {
    margin-bottom: 14px;
}
.solution-diff .line-add {
    animation: diffAddPulse 0.6s 0.2s 2 both;
}
.solution-diff .line-rem {
    animation: diffRemPulse 0.6s 0.2s 2 both;
}
@keyframes diffRemPulse {
    0%   { background: color-mix(in srgb, var(--danger) 22%, transparent); }
    50%  { background: color-mix(in srgb, var(--danger) 55%, transparent); }
    100% { background: color-mix(in srgb, var(--danger) 22%, transparent); }
}

/* Typewriter for scene 3 */
.scene-solve.active .mock-type .typed {
    display: inline-block;
    overflow: hidden;
    white-space: nowrap;
    vertical-align: bottom;
    animation: typeIn 2s steps(5) 0.6s both;
}

@keyframes typeIn {
    from { max-width: 0; }
    to   { max-width: 6ch; }
}

.scene-solve.active .mock-type .typed {
    max-width: 0;
}

.cursor-blink {
    display: inline-block;
    width: 2px;
    height: 1em;
    background: currentColor;
    vertical-align: bottom;
    animation: blink 0.7s steps(1) infinite;
}

@keyframes blink { 50% { opacity: 0; } }

.mock-btn-row {
    display: flex;
    gap: 8px;
    margin-bottom: 14px;
}

.scene-solve.active .mock-submit { animation: buttonPulse 0.5s 3s both; }
.scene-solve.active .mock-next   { animation: buttonPulse 0.5s 6.1s both; }
@keyframes buttonPulse {
    0%, 100% { transform: scale(1); }
    50%      { transform: scale(0.94); box-shadow: 0 0 0 4px color-mix(in srgb, var(--accent) 35%, transparent); }
}

.mock-result {
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-left: 4px solid var(--success);
    border-radius: 6px;
    padding: 12px 14px;
    opacity: 0;
    transform: translateY(10px);
}

.scene-solve.active .mock-result { animation: resultSlide 0.6s 4s both; }
@keyframes resultSlide {
    from { opacity: 0; transform: translateY(10px); }
    to   { opacity: 1; transform: translateY(0); }
}

.mock-result-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 6px;
}

.mock-result-badge {
    background: var(--success);
    color: #0d2a14;
    padding: 3px 10px;
    border-radius: 4px;
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.5px;
}

.mock-result-title { font-size: 0.88rem; color: var(--text-secondary); }

.mock-result-body {
    margin: 0;
    font-family: 'Consolas', 'Monaco', monospace;
    background: var(--bg-primary);
    padding: 8px 10px;
    border-radius: 4px;
    font-size: 0.85rem;
}

.scene-solve.active .mock-tree-check { opacity: 0; animation: checkIn 0.4s 4.6s both; }
@keyframes checkIn { from { opacity: 0; transform: scale(0); } to { opacity: 1; transform: scale(1); } }


/* --- Scene 4: give up --- */
.mock-solution-label {
    display: flex;
    gap: 10px;
    align-items: center;
    margin-bottom: 6px;
    opacity: 0;
}

.giveup-flip.flipped .mock-solution-label { animation: fadeSlideUp 0.5s 0.5s both; }

.mock-solution-badge {
    background: var(--danger);
    color: #fff;
    padding: 3px 10px;
    border-radius: 4px;
    font-size: 0.72rem;
    font-weight: 700;
    letter-spacing: 1px;
}

.mock-solution-hint { font-size: 0.82rem; color: var(--text-secondary); }

.mock-editor-locked {
    border-color: var(--danger) !important;
    opacity: 0.92;
}

@keyframes lockFade {
    from { border-color: var(--border); }
    to   { border-color: var(--danger); }
}

.mock-giveup-btn.giveup-btn-pulse { animation: pulseRed 0.5s 2 both; }
@keyframes pulseRed {
    0%, 100% { box-shadow: 0 0 0 0 color-mix(in srgb, var(--danger) 70%, transparent); }
    50%      { box-shadow: 0 0 0 10px color-mix(in srgb, var(--danger) 0%, transparent); }
}

.scene-giveup .mock-tree-cross { opacity: 0; color: var(--danger); }

/* Give up flip card */
.giveup-flip {
    perspective: 1400px;
    margin-bottom: 12px;
}
.giveup-flip-inner {
    position: relative;
    display: grid;
    grid-template-areas: "stack";
    transform-style: preserve-3d;
    transition: transform 0.9s cubic-bezier(0.3, 0.1, 0.2, 1);
}
.giveup-flip.flipped .giveup-flip-inner {
    transform: rotateY(180deg);
}
.giveup-flip.no-animate .giveup-flip-inner {
    transition: none;
}
.giveup-flip-face {
    grid-area: stack;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
}
.giveup-flip-back {
    transform: rotateY(180deg);
}

.cursor-giveup {
    top: 0;
    left: 0;
}
.cursor-giveup.cursor-clicking {
    animation: cursorClick 0.35s ease-out;
}

.scene-solve .cursor-solve {
    top: 0;
    left: 0;
}
.cursor-solve.cursor-clicking {
    animation: cursorClick 0.35s ease-out;
}

/* Scene 5 cursor (positions are JS-driven) */
.scene-bonus .cursor-bonus {
    top: 0;
    left: 0;
}
.cursor-bonus.cursor-clicking {
    animation: cursorClick 0.35s ease-out;
}
.scene-bonus .mock-app-bonus { position: relative; }

/* Flip used on the real challenge page */
.challenge-flip {
    margin-bottom: 14px;
}
.challenge-flip .giveup-flip-front,
.challenge-flip .giveup-flip-back {
    min-height: 120px;
}

.buggy-snapshot {
    position: absolute;
    left: -9999px;
    width: 1px;
    height: 1px;
    opacity: 0;
    pointer-events: none;
}


/* --- Scene 5: bonus --- */
.mock-app-bonus {
    padding: 22px 26px;
    min-height: 520px;
}

.mock-bonus-header {
    display: flex;
    align-items: center;
    gap: 10px;
    margin-bottom: 18px;
}

.mock-bonus-header h2 { margin: 0; font-size: 1.2rem; }
.mock-bonus-icon { font-size: 1.6rem; }

.mock-pills {
    display: flex;
    gap: 10px;
    margin-bottom: 22px;
    padding-bottom: 14px;
    border-bottom: 1px solid var(--border);
}

.mock-pill {
    background: var(--bg-secondary);
    color: var(--text-secondary);
    border: 1px solid var(--border);
    border-radius: 999px;
    padding: 8px 18px;
    font-size: 0.85rem;
    font-weight: 600;
    letter-spacing: 0.5px;
    text-transform: uppercase;
    cursor: pointer;
    transition: all 0.15s ease;
}

.mock-pill.pill-active {
    color: #ffffff;
    border-color: transparent;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.25);
}

.mock-pill-trap.pill-active   { background-color: #f1c40f; color: #3a2e00; }
.mock-pill-rule.pill-active   { background-color: #3498db; }
.mock-pill-gotcha.pill-active { background-color: var(--danger); }
.mock-pill-tip.pill-active    { background-color: var(--success); color: #0d2a14; }

.mock-bonus-stack {
    display: grid;
    grid-template-columns: 1fr;
    gap: 14px;
    max-width: 720px;
    margin: 0 auto;
}

.mock-bonus-card {
    grid-row: 1;
    grid-column: 1;
    align-self: start;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 14px 18px;
    border-left: 6px solid var(--border);
}

.mock-bonus-card h3 { margin: 8px 0 6px; font-size: 1rem; }
.mock-bonus-card p  { margin: 0; font-size: 0.88rem; color: var(--text-secondary); line-height: 1.5; }
.mock-bonus-card code { background: var(--bg-primary); padding: 1px 6px; border-radius: 3px; color: var(--accent); font-size: 0.82em; }

.card-trap   { border-left-color: #f1c40f; background: color-mix(in srgb, #f1c40f 10%, var(--bg-secondary)); }
.card-rule   { border-left-color: #3498db; background: color-mix(in srgb, #3498db 10%, var(--bg-secondary)); }
.card-gotcha { border-left-color: var(--danger); background: color-mix(in srgb, var(--danger) 10%, var(--bg-secondary)); }
.card-tip    { border-left-color: var(--success); background: color-mix(in srgb, var(--success) 10%, var(--bg-secondary)); }

.mock-card-badge {
    display: inline-block;
    padding: 3px 8px;
    border-radius: 4px;
    font-size: 0.7rem;
    font-weight: 700;
    letter-spacing: 0.5px;
}

.mock-bg-trap   { background: #f1c40f; color: #3a2e00; }
.mock-bg-rule   { background: #3498db; color: #fff; }
.mock-bg-gotcha { background: var(--danger); color: #fff; }
.mock-bg-tip    { background: var(--success); color: #0d2a14; }

/* Cards revealed by cursor clicks on pills — all overlap in row 1 of the grid,
   so the visible card always appears at the same vertical position regardless of
   which pill is clicked. Quiz auto-places into row 2. */
.mock-bonus-card {
    opacity: 0;
    visibility: hidden;
    transition: opacity 0.35s ease, visibility 0s linear 0.35s;
}
.mock-bonus-card.card-visible {
    opacity: 1;
    visibility: visible;
    transition: opacity 0.35s ease, visibility 0s linear 0s;
}

/* Quiz flip — visible in last part */
.mock-quiz {
    perspective: 1600px;
    margin-top: 6px;
    opacity: 0;
}

.mock-quiz { transition: opacity 0.35s ease; }
.mock-quiz.quiz-visible { opacity: 1; }

.mock-quiz-inner {
    position: relative;
    display: grid;
    transform-style: preserve-3d;
    transition: transform 0.7s;
}

.mock-quiz.flipped .mock-quiz-inner { transform: rotateY(180deg); }

.mock-quiz-front, .mock-quiz-back {
    grid-area: 1 / 1;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    background: color-mix(in srgb, var(--success) 10%, var(--bg-secondary));
    border: 1px solid var(--border);
    border-left: 6px solid var(--success);
    border-radius: 10px;
    padding: 18px 20px;
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.mock-quiz-front h3 { margin: 6px 0; font-size: 1.05rem; }
.mock-quiz-front em { text-transform: uppercase; font-style: normal; }
.mock-quiz-front p  { margin: 0; font-size: 0.88rem; color: var(--text-secondary); }
.mock-quiz-front .mock-btn { align-self: flex-start; margin-top: 8px; }

.mock-quiz-back { transform: rotateY(180deg); }

.mock-quiz-q { font-size: 0.95rem; margin: 4px 0 8px; }
.mock-quiz-q code { background: var(--bg-primary); padding: 1px 6px; border-radius: 3px; color: var(--accent); }

.mock-quiz-options { list-style: none; padding: 0; margin: 0; display: flex; flex-direction: column; gap: 6px; }

.mock-opt {
    position: relative;
    padding: 8px 12px 8px 40px;
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 6px;
    font-size: 0.88rem;
}

.mock-opt::before {
    content: attr(data-letter);
    position: absolute;
    left: 10px; top: 50%;
    transform: translateY(-50%);
    width: 22px; height: 22px;
    border-radius: 50%;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    display: flex; align-items: center; justify-content: center;
    font-weight: 700;
    font-size: 0.74rem;
    color: var(--text-secondary);
}

.mock-opt { transition: background 0.3s ease, border-color 0.3s ease; }
.mock-opt::before { transition: background 0.3s ease, border-color 0.3s ease, color 0.3s ease; }

.mock-opt-chosen.opt-wrong {
    background: color-mix(in srgb, var(--danger) 20%, var(--bg-primary));
    border-color: var(--danger);
}
.mock-opt-chosen.opt-wrong::before {
    content: "\2717";
    background: var(--danger);
    color: #fff;
    border-color: var(--danger);
}

.mock-opt[data-letter="D"].opt-correct {
    background: color-mix(in srgb, var(--success) 18%, var(--bg-primary));
    border-color: var(--success);
}
.mock-opt[data-letter="D"].opt-correct::before {
    content: "\2713";
    background: var(--success);
    color: #0d2a14;
    border-color: var(--success);
}

.mock-quiz-explain {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-left: 4px solid var(--accent);
    padding: 10px 12px;
    border-radius: 6px;
    font-size: 0.84rem;
    color: var(--text-secondary);
    line-height: 1.5;
    opacity: 0;
}

.mock-quiz-explain strong {
    display: block;
    text-transform: uppercase;
    font-size: 0.7rem;
    letter-spacing: 1px;
    color: var(--text-primary);
    margin-bottom: 4px;
}

.mock-quiz-explain { transition: opacity 0.4s ease; }
.mock-quiz-explain.explain-shown { opacity: 1; }


/* --- Scene 6: ready --- */
.scene-ready {
    text-align: center;
    padding: 40px 20px;
}

.scene-ready-box {
    max-width: 720px;
    margin: 0 auto;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 16px;
    padding: 40px 44px;
    box-shadow: 0 30px 60px -20px rgba(0, 0, 0, 0.5);
}

.scene-ready-title {
    font-size: 2.4rem;
    margin: 0 0 10px;
    font-weight: 800;
    background: linear-gradient(120deg, var(--text-primary), var(--accent));
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
}

.scene-ready-sub {
    color: var(--text-secondary);
    font-size: 1rem;
    margin: 0 0 28px;
    line-height: 1.55;
}

.ready-progress {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    border-radius: 10px;
    padding: 16px;
    margin-bottom: 26px;
    text-align: left;
}

.ready-counters {
    display: flex;
    justify-content: space-between;
    font-size: 0.9rem;
    margin-bottom: 10px;
}

.ready-counter-solved  { color: var(--success); font-weight: 600; }
.ready-counter-givenup { color: var(--danger); font-weight: 600; }
.ready-counter-total   { color: var(--text-secondary); }

.ready-bar {
    height: 14px;
    background: var(--bg-secondary);
    border-radius: 7px;
    overflow: hidden;
    position: relative;
}

.ready-split {
    position: absolute;
    left: 0; top: 0; bottom: 0;
    width: 0%;
    background: linear-gradient(90deg, var(--success) 0 80%, var(--danger) 80% 100%);
}

.scene-ready.active .ready-split {
    animation: readyGrow 2s 0.4s ease-out both;
}

@keyframes readyGrow {
    to { width: 75%; }
}

.scene-ready.active .ready-num-solved {
    animation: countSolved 2s 0.4s ease-out both;
}

.scene-ready.active .ready-num-givenup {
    animation: countGivenup 2s 0.4s ease-out both;
}

@keyframes countSolved { from { opacity: 0.4; } to { opacity: 1; } }
@keyframes countGivenup { from { opacity: 0.4; } to { opacity: 1; } }

.ready-cta { margin-bottom: 14px; }

.tutor-start-btn {
    display: inline-block;
    background: var(--accent);
    color: #fff;
    padding: 14px 34px;
    border-radius: 10px;
    font-size: 1.05rem;
    font-weight: 700;
    text-decoration: none;
    box-shadow: 0 10px 30px -10px color-mix(in srgb, var(--accent) 70%, transparent);
    transition: transform 0.15s ease, box-shadow 0.15s ease;
}

.tutor-start-btn:hover {
    transform: translateY(-2px);
    box-shadow: 0 14px 36px -10px color-mix(in srgb, var(--accent) 85%, transparent);
}

.scene-ready-hint {
    color: var(--text-secondary);
    font-size: 0.85rem;
    margin-top: 18px;
}

.ready-help-pill {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    padding: 1px 8px;
    border-radius: 999px;
    font-weight: 700;
    font-family: monospace;
}

/* --- Controls --- */
.tutor-controls {
    position: fixed;
    bottom: 0; left: 0; right: 0;
    background: color-mix(in srgb, var(--bg-secondary) 96%, transparent);
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    border-top: 1px solid var(--border);
    padding: 16px 24px 18px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    z-index: 100;
}

.tutor-narration {
    display: flex;
    align-items: center;
    gap: 16px;
    max-width: 1100px;
    margin: 0 auto;
    width: 100%;
}

.tutor-step-counter {
    background: var(--accent);
    color: #fff;
    padding: 4px 12px;
    border-radius: 999px;
    font-size: 0.75rem;
    font-weight: 700;
    letter-spacing: 0.5px;
    flex-shrink: 0;
}

.tutor-step-text { flex: 1; min-width: 0; }
.tutor-step-text h3 { margin: 0 0 2px; font-size: 1rem; }
.tutor-step-text p  { margin: 0; font-size: 0.85rem; color: var(--text-secondary); line-height: 1.4; }

.tutor-dots {
    display: flex;
    gap: 6px;
    justify-content: center;
    max-width: 1100px;
    margin: 0 auto;
    width: 100%;
}

.tutor-dot {
    width: 8px; height: 8px;
    background: var(--border);
    border-radius: 50%;
    transition: all 0.2s ease;
}

.tutor-dot.active {
    background: var(--accent);
    width: 24px;
    border-radius: 4px;
}

.tutor-buttons {
    display: flex;
    gap: 8px;
    justify-content: center;
    align-items: center;
    max-width: 1100px;
    margin: 0 auto;
    width: 100%;
}

.tutor-ctrl {
    background: var(--bg-primary);
    border: 1px solid var(--border);
    color: var(--text-primary);
    padding: 8px 16px;
    border-radius: 6px;
    font-size: 0.95rem;
    cursor: pointer;
    min-width: 44px;
    text-decoration: none;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    transition: all 0.15s ease;
}

.tutor-ctrl:hover {
    border-color: var(--accent);
    color: var(--accent);
}

.tutor-ctrl-play {
    background: var(--accent);
    color: #fff;
    border-color: transparent;
    font-size: 0.9rem;
    min-width: 50px;
}

.tutor-ctrl-play:hover { color: #fff; filter: brightness(1.1); }

.tutor-skip {
    margin-left: 16px;
    background: transparent;
    color: var(--text-secondary);
    font-size: 0.85rem;
    padding: 8px 14px;
}

.tutor-progress-line {
    height: 3px;
    background: var(--border);
    border-radius: 0;
    max-width: 1100px;
    margin: 0 auto;
    width: 100%;
    overflow: hidden;
    position: absolute;
    top: 0; left: 50%;
    transform: translateX(-50%);
}

.tutor-progress-fill {
    height: 100%;
    background: var(--accent);
    width: 0%;
    transition: none;
}

/* --- Help launcher on main pages --- */
.tutor-help-btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 36px;
    height: 36px;
    border-radius: 50%;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    color: var(--text-secondary);
    font-weight: 700;
    font-family: monospace;
    text-decoration: none;
    cursor: pointer;
    margin-right: 10px;
    font-size: 1rem;
    transition: all 0.15s ease;
}

.tutor-help-btn:hover {
    color: var(--accent);
    border-color: var(--accent);
    transform: scale(1.08);
}

/* ============================================================
   Metallic Gold Polish (overrides on top of base rules)
   ============================================================ */

body::before {
    content: '';
    position: fixed;
    inset: 0;
    z-index: -2;
    background:
        radial-gradient(ellipse 70% 50% at 30% 0%, var(--accent-soft), transparent 60%),
        radial-gradient(ellipse 50% 40% at 80% 100%, var(--accent-soft), transparent 65%),
        var(--bg-primary);
    transition: background 0.3s ease;
    pointer-events: none;
}

.header {
    background: var(--header-bg);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
}
.header h1 {
    font-size: 1.75rem;
    font-weight: 700;
    letter-spacing: -0.01em;
    background: var(--title-gradient);
    -webkit-background-clip: text;
    background-clip: text;
    color: transparent;
    display: flex;
    align-items: center;
    gap: 14px;
}
.header h1::before {
    content: '';
    width: 36px; height: 36px;
    border-radius: 10px;
    background: conic-gradient(from 220deg, var(--accent), var(--accent-deep), var(--metal-2), var(--accent));
    box-shadow: 0 0 22px var(--accent-glow), inset 0 0 0 1px var(--metal-edge);
    flex-shrink: 0;
    -webkit-background-clip: border-box;
    background-clip: border-box;
}

.btn-primary {
    background: var(--accent-brushed);
    color: #ffffff;
    border: 1px solid var(--accent);
    text-shadow: 0 1px 0 rgba(0, 0, 0, 0.25);
    box-shadow:
        inset 0 1px 0 rgba(255, 255, 255, 0.40),
        inset 0 -1px 0 rgba(0, 0, 0, 0.18),
        0 0 16px var(--accent-soft),
        0 4px 14px rgba(0, 0, 0, 0.30);
    font-weight: 600;
    transition: all .15s ease, transform .1s ease;
}
.btn-primary:hover {
    background: var(--accent-brushed-hover);
    color: #ffffff;
    box-shadow:
        inset 0 1px 0 rgba(255, 255, 255, 0.50),
        inset 0 -1px 0 rgba(0, 0, 0, 0.18),
        0 0 26px var(--accent-glow),
        0 6px 18px rgba(0, 0, 0, 0.40);
}
.btn-primary:active { transform: translateY(1px); }

.btn-bonus {
    background: transparent;
    color: var(--accent);
    border: 1px solid var(--accent);
    font-weight: 600;
    transition: all .15s ease;
}
.btn-bonus:hover {
    background: var(--accent-bg-subtle);
    color: var(--accent-hover);
    box-shadow: 0 0 16px var(--accent-soft);
}

.card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 14px;
    backdrop-filter: blur(12px);
    -webkit-backdrop-filter: blur(12px);
    transition: border-color .25s ease, box-shadow .25s ease, transform .25s ease;
}
.card:hover {
    border-color: var(--border-strong);
    box-shadow: 0 0 24px var(--accent-soft);
}

::-webkit-scrollbar { width: 10px; height: 10px; }
::-webkit-scrollbar-track { background: var(--bg-primary); }
::-webkit-scrollbar-thumb {
    background: linear-gradient(180deg, var(--metal-2), var(--metal-1));
    border-radius: 8px;
    border: 2px solid var(--bg-primary);
}
::-webkit-scrollbar-thumb:hover {
    background: linear-gradient(180deg, var(--accent-deep), var(--metal-2));
}

/* ============================================================
   Section Card (new index layout)
   ============================================================ */

.section-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 18px;
    padding: 0;
    margin-bottom: 18px;
    backdrop-filter: blur(14px);
    -webkit-backdrop-filter: blur(14px);
    box-shadow: var(--section-card-shadow);
    transition: border-color .25s ease, box-shadow .25s ease, transform .25s ease;
    position: relative;
    overflow: hidden;
}
.section-card::before {
    content: '';
    position: absolute;
    inset: 0 0 auto 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--accent), transparent);
    opacity: 0.55;
}
.section-card::after {
    content: '';
    position: absolute;
    left: 0; right: 0; bottom: 0;
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--accent), transparent);
    opacity: 0.30;
    transition: opacity .25s ease;
}
.section-card:hover {
    border-color: var(--border-strong);
    box-shadow: 0 16px 40px rgba(0, 0, 0, 0.40), 0 0 32px var(--accent-soft);
}
.section-card:hover::after { opacity: 0.85; }

.section-card-head {
    display: flex;
    align-items: center;
    gap: 16px;
    padding: 18px 22px;
    border-bottom: 1px solid var(--border);
}

.section-card-number {
    width: 44px; height: 44px;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 12px;
    background: conic-gradient(from 220deg, var(--accent), var(--accent-deep), var(--metal-2), var(--accent));
    color: #ffffff;
    font-family: var(--font-mono);
    font-size: 1.05rem;
    font-weight: 700;
    box-shadow: 0 0 16px var(--accent-soft), inset 0 0 0 1px var(--metal-edge);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.45);
}

.section-card-title-block { flex: 1; min-width: 0; }
.section-card-title {
    font-size: 1.20rem;
    font-weight: 600;
    color: var(--text-primary);
    margin: 0 0 5px 0;
    letter-spacing: -0.01em;
}
.section-card-meta {
    display: flex;
    align-items: center;
    gap: 14px;
    font-family: var(--font-mono);
    font-size: 0.78rem;
    color: var(--text-secondary);
    letter-spacing: 0.04em;
    flex-wrap: wrap;
}
.section-card-meta .stat-total   { color: var(--accent); }
.section-card-meta .stat-solved  { color: var(--success); }
.section-card-meta .stat-givenup { color: var(--danger); }

.section-card-actions {
    display: flex;
    gap: 8px;
    align-items: center;
    flex-shrink: 0;
    margin: 0;
}
.section-card-actions .btn { padding: 9px 18px; }

.section-card-list {
    list-style: none;
    margin: 0;
    padding: 14px 16px 18px;
    display: grid;
    gap: 8px;
}
.section-card-item {
    display: flex;
    align-items: center;
    gap: 14px;
    padding: 11px 16px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 10px;
    color: var(--text-primary);
    text-decoration: none;
    cursor: pointer;
    font-size: 0.92rem;
    width: 100%;
    text-align: left;
    transition: border-color .15s ease, background-color .15s ease, transform .12s ease, box-shadow .15s ease;
}
.section-card-item:hover {
    border-color: var(--border-strong);
    background: var(--accent-bg-subtle);
    transform: translateX(2px);
    box-shadow: 0 0 16px var(--accent-soft);
}
.section-card-item:active { transform: translateX(2px) translateY(1px); }

/* Status dot — empty / green / red */
.status-dot {
    width: 14px;
    height: 14px;
    border-radius: 50%;
    flex-shrink: 0;
    border: 2px solid var(--text-secondary);
    background: transparent;
    box-sizing: border-box;
    transition: all .15s ease;
}
.status-dot.todo {
    border-color: var(--text-secondary);
    opacity: 0.55;
    background: transparent;
}
.status-dot.completed {
    border-color: var(--success);
    background: var(--success);
    box-shadow: 0 0 10px rgba(80, 250, 123, 0.55), inset 0 0 4px rgba(255, 255, 255, 0.35);
}
.status-dot.givenup {
    border-color: var(--danger);
    background: var(--danger);
    box-shadow: 0 0 10px rgba(255, 85, 85, 0.55), inset 0 0 4px rgba(255, 255, 255, 0.35);
}
.section-card-item:hover .status-dot.todo {
    border-color: var(--accent);
    opacity: 0.9;
}

.section-card-item .item-title {
    flex: 1;
    min-width: 0;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    color: var(--text-primary);
    font-weight: 500;
}
.section-card-item .item-topic {
    color: var(--text-secondary);
    font-size: 0.76rem;
    font-family: var(--font-mono);
    flex-shrink: 0;
    opacity: 0.85;
}
.section-card-item .item-arrow {
    color: var(--text-secondary);
    font-size: 1rem;
    flex-shrink: 0;
    opacity: 0.40;
    transition: opacity .15s ease, transform .15s ease, color .15s ease;
}
.section-card-item:hover .item-arrow {
    color: var(--accent);
    opacity: 1;
    transform: translateX(3px);
}

/* Refined head alignment */
.section-card-head {
    align-items: stretch;
}
.section-card-title-block {
    display: flex;
    flex-direction: column;
    justify-content: center;
    gap: 4px;
}

@media (max-width: 720px) {
    .section-card-head { flex-wrap: wrap; }
    .section-card-actions { width: 100%; }
    .section-card-actions .btn { flex: 1; }
}

/* ============================================================
   Tutorial mock — section-card preview (Scene 2)
   ============================================================ */

.mock-section-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 14px;
    margin-bottom: 12px;
    overflow: hidden;
    position: relative;
    box-shadow: 0 8px 24px rgba(0, 0, 0, 0.40);
}
.mock-section-card::before {
    content: '';
    position: absolute;
    inset: 0 0 auto 0;
    height: 1px;
    background: linear-gradient(90deg, transparent, var(--accent), transparent);
    opacity: 0.55;
    pointer-events: none;
}
.mock-section-card::after {
    content: '';
    position: absolute;
    left: 0; right: 0; bottom: 0;
    height: 2px;
    background: linear-gradient(90deg, transparent, var(--accent), transparent);
    opacity: 0.30;
    pointer-events: none;
}

.mock-section-head {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 14px;
    border-bottom: 1px solid var(--border);
}

.mock-section-num {
    width: 32px; height: 32px;
    flex-shrink: 0;
    display: flex;
    align-items: center;
    justify-content: center;
    border-radius: 9px;
    background: conic-gradient(from 220deg, var(--accent), var(--accent-deep), var(--metal-2), var(--accent));
    color: #ffffff;
    font-family: var(--font-mono);
    font-size: 0.85rem;
    font-weight: 700;
    box-shadow: 0 0 12px var(--accent-soft), inset 0 0 0 1px var(--metal-edge);
    text-shadow: 0 1px 2px rgba(0, 0, 0, 0.45);
}

.mock-section-title-block { flex: 1; min-width: 0; }
.mock-section-title {
    font-size: 1rem;
    font-weight: 600;
    margin: 0 0 2px 0;
    color: var(--text-primary);
}
.mock-section-meta {
    font-family: var(--font-mono);
    font-size: 0.70rem;
    color: var(--accent);
    letter-spacing: 0.04em;
}

.mock-section-actions {
    display: flex;
    gap: 6px;
    flex-shrink: 0;
}
.mock-section-actions .mock-btn {
    padding: 5px 12px;
    font-size: 0.78rem;
}

.mock-section-list {
    padding: 8px 10px 10px;
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.mock-section-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 8px 12px;
    background: var(--bg-secondary);
    border: 1px solid var(--border);
    border-radius: 8px;
    text-decoration: none;
    color: var(--text-primary);
    font-size: 0.83rem;
    cursor: pointer;
    transition: border-color .15s ease, background-color .15s ease, transform .12s ease;
}
.mock-section-item:hover {
    border-color: var(--border-strong);
    background: var(--accent-bg-subtle);
    transform: translateX(2px);
}

.mock-status-dot {
    width: 11px;
    height: 11px;
    border-radius: 50%;
    flex-shrink: 0;
    border: 2px solid var(--text-secondary);
    background: transparent;
    box-sizing: border-box;
    transition: all .15s ease;
}
.mock-status-dot.todo {
    border-color: var(--text-secondary);
    opacity: 0.55;
    background: transparent;
}
.mock-status-dot.completed {
    border-color: var(--success);
    background: var(--success);
    box-shadow: 0 0 8px rgba(80, 250, 123, 0.55), inset 0 0 3px rgba(255, 255, 255, 0.35);
}
.mock-status-dot.givenup {
    border-color: var(--danger);
    background: var(--danger);
    box-shadow: 0 0 8px rgba(255, 85, 85, 0.55), inset 0 0 3px rgba(255, 255, 255, 0.35);
}

.mock-item-title {
    flex: 1;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
    font-weight: 500;
}
.mock-item-topic {
    color: var(--text-secondary);
    font-size: 0.7rem;
    font-family: var(--font-mono);
    flex-shrink: 0;
    opacity: 0.85;
}
.mock-item-arrow {
    color: var(--text-secondary);
    font-size: 0.85rem;
    flex-shrink: 0;
    opacity: 0.40;
}

/* ============================================================
   GitHub auth — Sign-in button + authed chip
   ============================================================ */

.github-signin {
    display: inline-flex;
    align-items: center;
    gap: 7px;
    padding: 6px 12px;
    border-radius: 8px;
    background: linear-gradient(180deg, var(--metal-2), var(--metal-1));
    border: 1px solid var(--border);
    color: var(--text-primary);
    text-decoration: none;
    font-size: 0.85rem;
    font-weight: 500;
    letter-spacing: 0.02em;
    box-shadow: inset 0 1px 0 rgba(255,255,255,0.06), 0 2px 6px rgba(0,0,0,0.30);
    transition: all .15s ease;
}
.github-signin:hover {
    border-color: var(--border-strong);
    color: var(--accent);
    box-shadow: inset 0 1px 0 rgba(255,255,255,0.08), 0 0 16px var(--accent-soft);
}
.github-signin svg { flex-shrink: 0; }

.github-chip {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 4px 6px 4px 4px;
    border-radius: 999px;
    background: linear-gradient(135deg, var(--metal-1), var(--metal-2) 60%, var(--metal-1));
    border: 1px solid var(--border);
    box-shadow: inset 0 1px 0 rgba(255,255,255,0.06), 0 2px 8px rgba(0,0,0,0.30);
}
.gh-avatar-wrap {
    position: relative;
    display: inline-flex;
    align-items: center;
    flex-shrink: 0;
}
.github-chip .gh-avatar {
    width: 24px; height: 24px;
    border-radius: 50%;
    border: 1px solid var(--accent);
    box-shadow: 0 0 6px var(--accent-soft);
    display: block;
}
.gh-sync-dot {
    position: absolute;
    right: -2px; bottom: -2px;
    width: 10px; height: 10px;
    border-radius: 50%;
    border: 2px solid var(--bg-primary);
    background: var(--text-secondary);
    transition: background-color .15s ease, box-shadow .15s ease;
    box-sizing: border-box;
}
.gh-sync-idle    { background: var(--text-secondary); }
.gh-sync-syncing { background: var(--warning); animation: ghSyncPulse 1.1s ease-in-out infinite; }
.gh-sync-success { background: var(--success); box-shadow: 0 0 6px rgba(80, 250, 123, 0.65); }
.gh-sync-error   { background: var(--danger);  box-shadow: 0 0 6px rgba(255, 94, 104, 0.65); }
@keyframes ghSyncPulse {
    0%, 100% { transform: scale(1);   opacity: 1; }
    50%      { transform: scale(1.3); opacity: 0.7; }
}

/* Sign-in disclosure modal */
.signin-modal {
    position: fixed;
    inset: 0;
    z-index: 1000;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(8, 6, 16, 0.65);
    backdrop-filter: blur(8px);
    -webkit-backdrop-filter: blur(8px);
    padding: 20px;
}
.signin-modal[hidden] { display: none; }
.signin-modal-box {
    background: var(--card-bg);
    border: 1px solid var(--border-strong);
    border-radius: 16px;
    box-shadow: 0 20px 60px rgba(0, 0, 0, 0.6), 0 0 32px var(--accent-soft);
    padding: 26px 28px 22px;
    max-width: 520px;
    width: 100%;
    color: var(--text-primary);
    backdrop-filter: blur(14px);
}
.signin-modal-title {
    margin: 0 0 14px;
    font-size: 1.2rem;
    font-weight: 700;
    color: var(--accent);
    text-shadow: 0 0 8px var(--accent-soft);
}
.signin-modal-body { font-size: 0.92rem; line-height: 1.55; color: var(--text-secondary); }
.signin-modal-body p { margin: 0 0 10px; }
.signin-modal-body code {
    font-family: var(--font-mono);
    font-size: 0.85em;
    background: var(--accent-bg-subtle);
    border: 1px solid var(--border);
    padding: 1px 6px;
    border-radius: 4px;
    color: var(--accent);
}
.signin-modal-actions {
    display: flex;
    gap: 10px;
    justify-content: flex-end;
    margin-top: 18px;
}
.github-chip .gh-login {
    color: var(--text-primary);
    font-size: 0.82rem;
    font-weight: 500;
    max-width: 130px;
    overflow: hidden;
    text-overflow: ellipsis;
    white-space: nowrap;
}
.github-chip .gh-action {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 22px; height: 22px;
    border-radius: 50%;
    color: var(--text-secondary);
    text-decoration: none;
    font-size: 0.85rem;
    border: 1px solid transparent;
    transition: all .15s ease;
}
.github-chip .gh-action:hover {
    color: var(--accent);
    background: var(--accent-bg-subtle);
    border-color: var(--border-strong);
}