/* 
  StudyNator v2.0 — Complete Design System, Themes, 3D Flip/Split Study, Multi-Nested Lego & Print Stylesheet (styles.css)
  Covers:
  - Light / Dark / Pure OLED (#000000) Themes
  - Horizontal (Wide 1160px) vs Vertical (800px) Responsive Layout
  - Home Smart Review Queue Banner, Subject Cards, Day Grid
  - 3D Flip Flashcard (.flashcard, .card-face, .is-flipped) & Split Comparison View (.split-study-card, .split-two-col, .split-one-col)
  - V11 Multi-Nested Lego Sentence Analyzer (.lego-node-box, .lego-children-container, Role Themes)
  - 5-Type Multi-Quiz, Cloze Blanks (.cloze-blank), 84-Day Grass Heatmap (.heatmap-grid), CLS-Guarded AdSense Slot
  - 2-Column A4 Printable Exam Sheet (@media print)
*/

:root {
    --primary: #4F46E5;
    --primary-hover: #4338CA;
    --secondary: #10B981;
    --danger: #EF4444;
    --warning: #F59E0B;

    --bg-main: #F3F4F6;
    --bg-surface: #FFFFFF;
    --text-main: #1F2937;
    --text-muted: #6B7280;
    --border-color: #E5E7EB;

    --shadow-sm: 0 1px 3px 0 rgba(15, 23, 42, 0.06);
    --shadow-md: 0 4px 12px -1px rgba(15, 23, 42, 0.08), 0 2px 4px -1px rgba(15, 23, 42, 0.04);
    --shadow-lg: 0 12px 24px -4px rgba(15, 23, 42, 0.12), 0 4px 8px -2px rgba(15, 23, 42, 0.06);

    --radius-md: 0.55rem;
    --radius-lg: 0.95rem;
    --radius-xl: 1.35rem;
    --font-size-base: 16px;
}

body.dark-mode {
    --primary: #6366F1;
    --primary-hover: #818CF8;
    --secondary: #34D399;
    --danger: #F87171;
    --warning: #FBBF24;

    --bg-main: #0F172A;
    --bg-surface: #1E293B;
    --text-main: #F8FAFC;
    --text-muted: #94A3B8;
    --border-color: #334155;
}

body.oled-mode {
    --primary: #6366F1;
    --primary-hover: #818CF8;
    --secondary: #34D399;
    --danger: #F87171;
    --warning: #FBBF24;

    --bg-main: #000000;
    --bg-surface: #070A10;
    --text-main: #FFFFFF;
    --text-muted: #9CA3AF;
    --border-color: #1F2937;
    --shadow-sm: none;
    --shadow-md: none;
    --shadow-lg: none;
}

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

html {
    font-size: var(--font-size-base);
}

body {
    background-color: var(--bg-main);
    color: var(--text-main);
    font-family: 'Pretendard', 'Inter', -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
    line-height: 1.55;
    transition: background-color 0.25s ease, color 0.25s ease;
    overflow-x: hidden;
    overscroll-behavior-y: none;
    -webkit-tap-highlight-color: transparent;
}

/* Layout Direction Container Width (#25) */
.app-container {
    max-width: 860px;
    margin: 0 auto;
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    position: relative;
    transition: max-width 0.25s ease;
}

body.layout-horizontal .app-container {
    max-width: 1180px;
}

body.layout-vertical .app-container {
    max-width: 820px;
}

main#view-layer {
    flex: 1;
    display: flex;
    flex-direction: column;
    padding: 1.15rem 1rem 3.5rem;
    animation: fadeIn 0.25s ease-out;
}

h1, h2, h3, h4 {
    margin-bottom: 0.4rem;
    font-weight: 700;
}

@keyframes fadeIn {
    from { opacity: 0; transform: translateY(6px); }
    to { opacity: 1; transform: translateY(0); }
}

.word-break-smart {
    word-break: keep-all;
    overflow-wrap: anywhere;
}

@media (max-width: 640px) {
    .hide-on-mobile {
        display: none !important;
    }
}

/* Buttons */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.35rem;
    padding: 0.68rem 1.25rem;
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    font-family: inherit;
    font-weight: 600;
    font-size: 0.95rem;
    cursor: pointer;
    transition: all 0.16s ease;
    user-select: none;
    white-space: nowrap;
}

.btn:active:not(:disabled) {
    transform: scale(0.98);
}

.btn:disabled {
    opacity: 0.52;
    cursor: not-allowed;
}

.btn-sm {
    padding: 0.45rem 0.85rem;
    font-size: 0.85rem;
}

.btn-xs {
    padding: 0.32rem 0.65rem;
    font-size: 0.78rem;
}

.btn-primary {
    background-color: var(--primary);
    color: #ffffff;
    box-shadow: var(--shadow-sm);
}

.btn-primary:hover:not(:disabled) {
    background-color: var(--primary-hover);
    box-shadow: var(--shadow-md);
}

.btn-secondary {
    background-color: var(--secondary);
    color: #ffffff;
}

.btn-outline {
    background-color: var(--bg-surface);
    border: 1.5px solid var(--border-color);
    color: var(--text-main);
}

.btn-outline:hover:not(:disabled) {
    border-color: var(--primary);
    color: var(--primary);
}

.btn-danger {
    background-color: var(--danger);
    color: #ffffff;
}

.icon-btn {
    background: transparent;
    border: none;
    font-size: 1.25rem;
    cursor: pointer;
    color: var(--text-main);
    padding: 0.4rem;
    border-radius: 50%;
    transition: background 0.15s ease;
    display: inline-flex;
    align-items: center;
    justify-content: center;
}

.icon-btn:hover {
    background: rgba(99, 102, 241, 0.12);
}

/* Header */
.app-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 0.75rem 1rem;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border-color);
    position: sticky;
    top: 0;
    z-index: 100;
    gap: 0.5rem;
}

.logo {
    font-size: 1.2rem;
    font-weight: 800;
    color: var(--primary);
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    user-select: none;
}

.version-pill {
    font-size: 0.7rem;
    padding: 0.12rem 0.45rem;
    border-radius: 999px;
    background: rgba(79, 70, 229, 0.14);
    color: var(--primary);
    font-weight: 700;
}

.header-actions {
    display: flex;
    align-items: center;
    gap: 0.4rem;
    flex-wrap: wrap;
}

.header-chip-btn {
    display: inline-flex;
    align-items: center;
    gap: 0.3rem;
    padding: 0.36rem 0.68rem;
    border-radius: 999px;
    border: 1px solid var(--border-color);
    background: var(--bg-main);
    color: var(--text-main);
    font-size: 0.8rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.15s ease;
}

.header-chip-btn:hover {
    border-color: var(--primary);
    color: var(--primary);
}

/* Home View & Smart Review Banner */
.smart-review-banner {
    background: linear-gradient(135deg, #4F46E5 0%, #0EA5E9 100%);
    color: #ffffff;
    padding: 1.15rem 1.35rem;
    border-radius: var(--radius-lg);
    margin-bottom: 1.35rem;
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 1rem;
    flex-wrap: wrap;
    box-shadow: var(--shadow-md);
}

.smart-review-badge {
    display: inline-block;
    font-size: 0.74rem;
    font-weight: 700;
    padding: 0.18rem 0.55rem;
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.2);
    margin-bottom: 0.35rem;
}

.smart-review-info h3 {
    font-size: 1.08rem;
    margin-bottom: 0.2rem;
}

.smart-review-info p {
    font-size: 0.84rem;
    opacity: 0.92;
}

.smart-review-actions {
    display: flex;
    gap: 0.5rem;
    flex-wrap: wrap;
}

.home-header-bar {
    display: flex;
    justify-content: space-between;
    align-items: flex-end;
    gap: 0.75rem;
    flex-wrap: wrap;
    margin-bottom: 1.25rem;
}

.home-quick-actions {
    display: flex;
    gap: 0.45rem;
    flex-wrap: wrap;
}

.subject-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(290px, 1fr));
    gap: 1rem;
}

.subject-card {
    background: var(--bg-surface);
    border: 1.5px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1.15rem;
    box-shadow: var(--shadow-sm);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    gap: 1rem;
    cursor: pointer;
    transition: transform 0.16s ease, border-color 0.16s ease, box-shadow 0.16s ease;
}

.subject-card:hover {
    transform: translateY(-2px);
    border-color: var(--primary);
    box-shadow: var(--shadow-md);
}

.subject-card.subject-pinned {
    border-color: var(--primary);
    border-width: 2px;
}

.subject-card-title {
    font-size: 1.12rem;
    margin: 0;
}

.subject-meta-badges {
    display: flex;
    flex-wrap: wrap;
    gap: 0.35rem;
    margin: 0.65rem 0;
}

.meta-pill {
    display: inline-flex;
    align-items: center;
    gap: 0.25rem;
    padding: 0.18rem 0.55rem;
    font-size: 0.74rem;
    font-weight: 700;
    border-radius: 999px;
    background: var(--bg-main);
    color: var(--text-muted);
    border: 1px solid var(--border-color);
}

.meta-pill.audio-pill {
    background: rgba(16, 185, 129, 0.12);
    color: var(--secondary);
    border-color: rgba(16, 185, 129, 0.3);
}

.meta-pill.lego-pill {
    background: rgba(245, 158, 11, 0.12);
    color: var(--warning);
    border-color: rgba(245, 158, 11, 0.3);
}

.meta-pill.wrong-pill {
    background: rgba(239, 68, 68, 0.12);
    color: var(--danger);
    border-color: rgba(239, 68, 68, 0.3);
}

.subject-progress-bar {
    width: 100%;
    height: 7px;
    background: var(--bg-main);
    border-radius: 999px;
    overflow: hidden;
}

.subject-progress-fill {
    height: 100%;
    background: var(--secondary);
    transition: width 0.3s ease;
}

.subject-card-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.5rem;
    padding-top: 0.75rem;
    border-top: 1px solid var(--border-color);
}

/* Subject Detail View */
.subject-main-action-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(170px, 1fr));
    gap: 0.65rem;
}

.subject-hero-btn {
    padding: 0.85rem 0.9rem;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 0.45rem;
    font-weight: 700;
}

.days-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: 0.85rem;
}

.day-card {
    background: var(--bg-surface);
    border: 1.5px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1rem;
    box-shadow: var(--shadow-sm);
    transition: transform 0.15s ease;
}

.day-card.day-completed {
    background: linear-gradient(135deg, #10B981, #059669);
    color: #ffffff;
    border-color: #059669;
}

/* Study View (#13, #15, #18, #22, #25, #26, #27) */
.study-toolbar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.5rem;
    flex-wrap: wrap;
    margin-bottom: 0.65rem;
}

.study-toolbar-switches {
    display: flex;
    align-items: center;
    gap: 0.35rem;
    flex-wrap: wrap;
}

.study-counter-pill {
    font-weight: 800;
    font-size: 0.95rem;
    color: var(--primary);
    padding: 0.25rem 0.65rem;
    border-radius: 999px;
    background: rgba(79, 70, 229, 0.1);
}

.btn-active-chip, .btn-active-audiobook {
    border-color: var(--primary) !important;
    background: rgba(79, 70, 246, 0.12) !important;
    color: var(--primary) !important;
}

.study-slider-row {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    margin-bottom: 0.85rem;
    padding: 0.35rem 0.65rem;
    background: var(--bg-surface);
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.study-range-slider {
    flex: 1;
    accent-color: var(--primary);
    cursor: pointer;
}

/* 3D Flip Flashcard Mode */
.flashcard-host.host-flip-mode {
    min-height: 360px;
    perspective: 1200px;
    margin-bottom: 1rem;
    position: relative;
}

.flashcard {
    width: 100%;
    min-height: 360px;
    position: relative;
    transition: transform 0.55s cubic-bezier(0.22, 1, 0.36, 1);
    transform-style: preserve-3d;
    cursor: pointer;
}

.flashcard.is-flipped {
    transform: rotateY(180deg);
}

.card-face {
    position: absolute;
    inset: 0;
    backface-visibility: hidden;
    -webkit-backface-visibility: hidden;
    border-radius: var(--radius-xl);
    padding: 1.5rem;
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    box-shadow: var(--shadow-md);
    overflow: hidden;
}

.card-front {
    background: var(--bg-surface);
    border: 2.5px solid var(--primary);
    color: var(--text-main);
}

.card-back {
    background: linear-gradient(145deg, var(--primary), #3730A3);
    color: #ffffff;
    transform: rotateY(180deg);
    border: 2.5px solid var(--primary);
}

.card-meta-top-left {
    display: flex;
    gap: 0.35rem;
    flex-wrap: wrap;
    padding-right: 2.5rem;
}

.card-num-badge, .card-audio-badge, .card-srs-badge, .card-wrong-badge {
    font-size: 0.72rem;
    font-weight: 700;
    padding: 0.16rem 0.5rem;
    border-radius: 999px;
    background: rgba(99, 102, 241, 0.14);
    color: var(--primary);
}

.card-back .card-num-badge,
.card-back .card-audio-badge,
.card-back .card-srs-badge,
.card-back .card-wrong-badge {
    background: rgba(255, 255, 255, 0.2);
    color: #ffffff;
}

.btn-star {
    position: absolute;
    top: 0.75rem;
    right: 0.75rem;
    font-size: 1.45rem;
    color: var(--warning);
    z-index: 10;
}

.card-scroll-body {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    overflow-y: auto;
    padding: 1rem 0.4rem;
}

.card-scroll-body h2 {
    font-size: 1.45rem;
    line-height: 1.45;
}

.card-back-explanation {
    font-size: 0.95rem;
    line-height: 1.55;
    background: rgba(0, 0, 0, 0.2);
    padding: 0.75rem 1rem;
    border-radius: var(--radius-md);
    width: 100%;
    text-align: left;
}

.card-bottom-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.5rem;
    padding-top: 0.5rem;
}

.card-flip-hint {
    font-size: 0.78rem;
    color: var(--text-muted);
}

/* Split Comparison Study Mode (#25) */
.split-study-card {
    display: grid;
    gap: 1rem;
    margin-bottom: 1rem;
}

.split-study-card.split-two-col {
    grid-template-columns: 1fr 1.15fr;
}

.split-study-card.split-one-col {
    grid-template-columns: 1fr;
}

@media (max-width: 768px) {
    .split-study-card.split-two-col {
        grid-template-columns: 1fr;
    }
}

.split-panel {
    background: var(--bg-surface);
    border: 2px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1.25rem;
    box-shadow: var(--shadow-sm);
    display: flex;
    flex-direction: column;
    justify-content: space-between;
    min-height: 240px;
    position: relative;
}

.split-problem-panel {
    border-color: var(--primary);
}

.split-panel-header {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    margin-bottom: 0.75rem;
}

.split-problem-body {
    flex: 1;
    display: flex;
    align-items: center;
    padding: 0.5rem 0;
}

.split-problem-body h2 {
    font-size: 1.32rem;
    line-height: 1.5;
}

.split-problem-actions {
    display: flex;
    gap: 0.5rem;
    margin-top: 0.75rem;
}

.split-concealed-cover {
    flex: 1;
    min-height: 200px;
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    gap: 0.45rem;
    text-align: center;
    cursor: pointer;
    border-radius: var(--radius-md);
    background: var(--bg-main);
    border: 1.5px dashed var(--primary);
    padding: 1.5rem;
}

.split-answer-title {
    color: var(--primary);
    font-size: 1.2rem;
    margin: 0;
}

.split-explanation-box {
    margin-top: 0.75rem;
    padding: 0.85rem;
    background: var(--bg-main);
    border-radius: var(--radius-md);
    font-size: 0.92rem;
    line-height: 1.6;
}

/* SRS Evaluation 3-Button Bar (#18) */
.srs-eval-bar {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 0.55rem;
    margin-bottom: 0.75rem;
}

.srs-btn {
    padding: 0.65rem 0.5rem;
    background: var(--bg-surface);
    border: 1.5px solid var(--border-color);
    color: var(--text-main);
    font-size: 0.86rem;
    display: flex;
    flex-direction: column;
    gap: 0.1rem;
}

.srs-sub-txt {
    font-size: 0.7rem;
    color: var(--text-muted);
    font-weight: 500;
}

.srs-btn-hard:hover { border-color: var(--danger); color: var(--danger); }
.srs-btn-good:hover { border-color: var(--warning); color: var(--warning); }
.srs-btn-easy:hover { border-color: var(--secondary); color: var(--secondary); }

.study-nav-bar {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 0.65rem;
    margin-bottom: 0.75rem;
}

.study-tools-bar {
    display: flex;
    gap: 0.45rem;
    flex-wrap: wrap;
}

.study-lego-btn {
    flex: 1.4;
}

.study-tool-btn {
    flex: 1;
}

.lego-cached-dot {
    font-size: 0.68rem;
    padding: 0.1rem 0.4rem;
    border-radius: 999px;
    background: rgba(255, 255, 255, 0.25);
    margin-left: 0.25rem;
}

/* Cloze Interactive Blank Button (#24) */
.cloze-blank {
    display: inline-flex;
    align-items: center;
    padding: 0.1rem 0.55rem;
    margin: 0 0.15rem;
    border-radius: 6px;
    border: 1.5px dashed var(--primary);
    background: rgba(79, 70, 229, 0.14);
    color: var(--primary);
    font-weight: 700;
    font-size: 0.88em;
    cursor: pointer;
    transition: all 0.15s ease;
}

.cloze-blank.revealed {
    border-style: solid;
    background: rgba(16, 185, 129, 0.18);
    border-color: var(--secondary);
    color: var(--secondary);
}

/* V11 Multi-Nested Lego Sentence Analyzer (#25, #27) */
.analyzer-top-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.65rem;
    flex-wrap: wrap;
    margin-bottom: 1rem;
}

.analyzer-title {
    font-size: 1.25rem;
    margin: 0;
    display: inline-flex;
    align-items: center;
    gap: 0.4rem;
}

.badge-v11 {
    font-size: 0.7rem;
    padding: 0.15rem 0.5rem;
    border-radius: 999px;
    background: linear-gradient(135deg, #4F46E5, #EC4899);
    color: #ffffff;
}

.sticky-structure-bar {
    position: sticky;
    top: 58px;
    z-index: 85;
    background: var(--bg-surface);
    border: 1.5px solid var(--primary);
    border-radius: var(--radius-md);
    padding: 0.5rem 0.75rem;
    margin-bottom: 1rem;
    display: flex;
    align-items: center;
    gap: 0.5rem;
    box-shadow: var(--shadow-sm);
    overflow-x: auto;
}

.sticky-bar-label {
    font-size: 0.76rem;
    font-weight: 800;
    color: var(--primary);
    white-space: nowrap;
}

.sticky-chips-scroll {
    display: flex;
    gap: 0.4rem;
    overflow-x: auto;
}

.structure-nav-chip {
    display: inline-flex;
    align-items: center;
    gap: 0.25rem;
    padding: 0.22rem 0.55rem;
    border-radius: 999px;
    font-size: 0.74rem;
    border: 1px solid var(--border-color);
    background: var(--bg-main);
    color: var(--text-main);
    cursor: pointer;
    white-space: nowrap;
}

.analyzer-input-card, .analysis-card {
    background: var(--bg-surface);
    border: 1.5px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1.15rem;
    margin-bottom: 1rem;
    box-shadow: var(--shadow-sm);
}

.analyzer-mode-tabs {
    display: flex;
    gap: 0.4rem;
    margin-bottom: 0.75rem;
}

.mode-tab-btn {
    padding: 0.4rem 0.85rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-main);
    color: var(--text-muted);
    font-size: 0.83rem;
    font-weight: 700;
    cursor: pointer;
}

.mode-tab-btn.active {
    background: var(--primary);
    color: #ffffff;
    border-color: var(--primary);
}

.linked-card-banner {
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 0.4rem;
    padding: 0.45rem 0.75rem;
    background: var(--bg-main);
    border-radius: var(--radius-md);
    font-size: 0.8rem;
    margin-bottom: 0.65rem;
}

.badge-cache-status.cached { color: var(--secondary); font-weight: 700; }
.badge-cache-status.uncached { color: var(--warning); font-weight: 700; }

.sentence-textarea-wrap {
    position: relative;
    margin-bottom: 0.75rem;
}

.analyzer-textarea {
    padding-right: 3.2rem !important;
    font-size: 1.05rem !important;
    line-height: 1.5;
}

.textarea-float-btns {
    position: absolute;
    right: 0.45rem;
    top: 0.45rem;
    display: flex;
    flex-direction: column;
    gap: 0.25rem;
}

.analyzer-input-actions {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.65rem;
    flex-wrap: wrap;
}

.example-gen-group {
    display: flex;
    align-items: center;
    gap: 0.35rem;
    flex-wrap: wrap;
}

.example-label {
    font-size: 0.8rem;
    color: var(--text-muted);
    font-weight: 600;
}

.analyzer-utility-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.5rem;
    flex-wrap: wrap;
    margin-bottom: 0.85rem;
}

.analyzer-tabs-nav {
    display: flex;
    gap: 0.4rem;
    overflow-x: auto;
    padding-bottom: 0.4rem;
    margin-bottom: 1rem;
}

.analyzer-tab-btn {
    padding: 0.48rem 0.9rem;
    border-radius: 999px;
    border: 1px solid var(--border-color);
    background: var(--bg-surface);
    color: var(--text-muted);
    font-size: 0.83rem;
    font-weight: 700;
    cursor: pointer;
    white-space: nowrap;
}

.analyzer-tab-btn.active {
    background: var(--primary);
    color: #ffffff;
    border-color: var(--primary);
}

.analysis-grid-2col {
    display: grid;
    grid-template-columns: 1.3fr 1fr;
    gap: 1rem;
}

@media (max-width: 768px) {
    .analysis-grid-2col {
        grid-template-columns: 1fr;
    }
}

.analysis-card-title {
    font-size: 1rem;
    font-weight: 800;
    color: var(--primary);
    margin-bottom: 0.75rem;
}

.trans-badge {
    display: inline-block;
    font-size: 0.72rem;
    font-weight: 800;
    padding: 0.12rem 0.5rem;
    border-radius: 4px;
    margin-bottom: 0.25rem;
}

.trans-badge.literal { background: rgba(99, 102, 241, 0.14); color: var(--primary); }
.trans-badge.natural { background: rgba(16, 185, 129, 0.14); color: var(--secondary); }

.cefr-level-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    font-size: 1.5rem;
    font-weight: 900;
    padding: 0.35rem 0.9rem;
    border-radius: var(--radius-md);
    background: rgba(79, 70, 229, 0.14);
    color: var(--primary);
    margin-bottom: 0.5rem;
}

/* Nested Lego Nodes (#25, #27) */
.lego-legend-pills {
    display: flex;
    gap: 0.35rem;
    flex-wrap: wrap;
}

.legend-dot {
    font-size: 0.74rem;
    font-weight: 700;
    padding: 0.15rem 0.5rem;
    border-radius: 6px;
}

.lego-node-box {
    border: 2px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 0.85rem;
    background: var(--bg-surface);
    margin: 0.45rem 0;
    transition: all 0.15s ease;
}

.lego-node-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 0.45rem;
    flex-wrap: wrap;
    margin-bottom: 0.45rem;
}

.lego-role-badge {
    font-size: 0.72rem;
    font-weight: 800;
    padding: 0.14rem 0.5rem;
    border-radius: 6px;
}

.lego-mini-btn {
    padding: 0.15rem 0.48rem;
    font-size: 0.72rem;
    font-weight: 700;
    border-radius: 6px;
    border: 1px solid var(--border-color);
    background: var(--bg-main);
    color: var(--text-main);
    cursor: pointer;
}

.lego-node-content {
    font-size: 1.02rem;
    font-weight: 700;
    margin-bottom: 0.35rem;
    cursor: pointer;
}

.lego-node-trans {
    font-size: 0.88rem;
    font-weight: 600;
    color: var(--text-main);
}

.lego-node-exp {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: 0.2rem;
}

.lego-children-container.children-horizontal {
    display: flex;
    flex-direction: row;
    flex-wrap: wrap;
    gap: 0.65rem;
    margin-top: 0.65rem;
    align-items: stretch;
}

.lego-children-container.children-horizontal > .lego-node-box {
    flex: 1 1 220px;
    margin: 0;
}

.lego-children-container.children-vertical {
    display: flex;
    flex-direction: column;
    gap: 0.55rem;
    margin-top: 0.6rem;
    padding-left: 0.75rem;
    border-left: 3px dashed var(--border-color);
}

.lego-children-container.collapsed {
    display: none !important;
}

/* Role Color Themes */
.lego-role-subject { border-color: #3B82F6; background: rgba(59, 130, 246, 0.06); }
.lego-role-subject > .lego-node-header .lego-role-badge { background: #3B82F6; color: #fff; }

.lego-role-verb { border-color: #EF4444; background: rgba(239, 68, 68, 0.06); }
.lego-role-verb > .lego-node-header .lego-role-badge { background: #EF4444; color: #fff; }

.lego-role-object { border-color: #10B981; background: rgba(16, 185, 129, 0.06); }
.lego-role-object > .lego-node-header .lego-role-badge { background: #10B981; color: #fff; }

.lego-role-modifier { border-color: #F59E0B; background: rgba(245, 158, 11, 0.06); }
.lego-role-modifier > .lego-node-header .lego-role-badge { background: #F59E0B; color: #fff; }

.lego-role-clause { border-color: #8B5CF6; background: rgba(139, 92, 246, 0.06); }
.lego-role-clause > .lego-node-header .lego-role-badge { background: #8B5CF6; color: #fff; }

.lego-role-root { border-color: var(--primary); }
.lego-role-root > .lego-node-header .lego-role-badge { background: var(--primary); color: #fff; }

/* Sequential, Structure, POS & Tutor */
.sequential-list {
    display: flex;
    flex-direction: column;
    gap: 0.5rem;
}

.sequential-row {
    display: flex;
    align-items: center;
    gap: 0.6rem;
    flex-wrap: wrap;
    padding: 0.45rem 0.65rem;
    border-radius: var(--radius-md);
    background: var(--bg-main);
}

.seq-chunk {
    display: inline-flex;
    align-items: center;
    gap: 0.35rem;
    padding: 0.25rem 0.6rem;
    border-radius: 6px;
    font-weight: 700;
    cursor: pointer;
}

.seq-role-tag {
    font-size: 0.7rem;
    padding: 0.08rem 0.35rem;
    border-radius: 4px;
    background: rgba(0, 0, 0, 0.15);
}

.tips-list {
    padding-left: 1.2rem;
    display: flex;
    flex-direction: column;
    gap: 0.45rem;
    font-size: 0.92rem;
}

.structure-detail-list {
    display: flex;
    flex-direction: column;
    gap: 0.65rem;
}

.structure-detail-item {
    padding: 0.85rem;
    border-radius: var(--radius-md);
    border-left: 4px solid var(--primary);
}

.pos-cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(210px, 1fr));
    gap: 0.75rem;
}

.pos-word-card {
    padding: 0.85rem;
    border-radius: var(--radius-md);
    background: var(--bg-main);
    border: 1px solid var(--border-color);
}

.pos-tag-badge {
    font-size: 0.72rem;
    font-weight: 700;
    padding: 0.12rem 0.45rem;
    border-radius: 4px;
    background: rgba(79, 70, 229, 0.14);
    color: var(--primary);
}

.btn-add-vocab-card {
    font-size: 0.74rem;
    font-weight: 700;
    padding: 0.2rem 0.55rem;
    border-radius: 6px;
    border: 1px solid var(--primary);
    background: var(--primary);
    color: #ffffff;
    cursor: pointer;
}

.btn-add-vocab-card.added {
    background: var(--secondary);
    border-color: var(--secondary);
}

.tutor-quick-chips {
    display: flex;
    gap: 0.4rem;
    flex-wrap: wrap;
    margin-bottom: 0.75rem;
}

.tutor-Preset-chip {
    padding: 0.35rem 0.7rem;
    border-radius: 999px;
    border: 1px solid var(--border-color);
    background: var(--bg-main);
    color: var(--text-main);
    font-size: 0.78rem;
    cursor: pointer;
}

.tutor-messages-box {
    max-height: 300px;
    overflow-y: auto;
    padding: 0.85rem;
    background: var(--bg-main);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    margin-bottom: 0.75rem;
    display: flex;
    flex-direction: column;
    gap: 0.65rem;
}

.tutor-bubble-row {
    display: flex;
}

.tutor-bubble-row.user-row { justify-content: flex-end; }
.tutor-bubble-row.model-row { justify-content: flex-start; }

.tutor-bubble {
    max-width: 85%;
    padding: 0.65rem 0.9rem;
    border-radius: var(--radius-md);
    font-size: 0.88rem;
}

.user-bubble { background: var(--primary); color: #ffffff; }
.model-bubble { background: var(--bg-surface); border: 1px solid var(--border-color); }

.tutor-input-row {
    display: flex;
    gap: 0.5rem;
}

.word-highlight {
    background: rgba(245, 158, 11, 0.35);
    color: inherit;
    padding: 0 2px;
    border-radius: 3px;
}

/* Quiz View (#19) */
.quiz-top-bar {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 1rem;
}

.speed-timer-wrap {
    width: 100%;
    height: 8px;
    background: var(--bg-surface);
    border-radius: 999px;
    overflow: hidden;
    margin-bottom: 1rem;
}

.speed-timer-bar {
    height: 100%;
    width: 100%;
    background: var(--danger);
    transition: width 0.1s linear;
}

.quiz-card-box {
    background: var(--bg-surface);
    padding: 1.5rem;
    border-radius: var(--radius-xl);
    box-shadow: var(--shadow-md);
    border: 1.5px solid var(--border-color);
}

.opt-num-badge {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 24px;
    height: 24px;
    border-radius: 50%;
    background: var(--bg-main);
    font-size: 0.8rem;
    font-weight: 800;
}

/* Search & Stats View (#17, #20) */
.search-chip-bar {
    display: flex;
    gap: 0.4rem;
    flex-wrap: wrap;
}

.filter-chip {
    padding: 0.32rem 0.75rem;
    border-radius: 999px;
    border: 1px solid var(--border-color);
    background: var(--bg-main);
    color: var(--text-muted);
    font-size: 0.8rem;
    font-weight: 700;
    cursor: pointer;
}

.filter-chip.active {
    background: var(--primary);
    color: #ffffff;
    border-color: var(--primary);
}

.search-result-card, .wrong-clinic-item {
    background: var(--bg-surface);
    padding: 1rem;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    cursor: pointer;
    transition: border-color 0.15s ease;
}

.search-result-card:hover {
    border-color: var(--primary);
}

.stats-kpi-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(200px, 1fr));
    gap: 0.85rem;
    margin-bottom: 1.25rem;
}

.stats-kpi-card {
    background: var(--bg-surface);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 1rem;
    display: flex;
    align-items: center;
    gap: 0.85rem;
    box-shadow: var(--shadow-sm);
}

.kpi-emoji { font-size: 2rem; }
.kpi-title { font-size: 0.78rem; color: var(--text-muted); font-weight: 600; }
.kpi-num { font-size: 1.35rem; font-weight: 800; color: var(--primary); }
.kpi-desc { font-size: 0.75rem; color: var(--text-muted); }

.heatmap-grid {
    display: grid;
    grid-template-columns: repeat(14, 1fr);
    gap: 5px;
}

@media (min-width: 640px) {
    .heatmap-grid {
        grid-template-columns: repeat(28, 1fr);
    }
}

.heatmap-cell {
    aspect-ratio: 1;
    border-radius: 3px;
    background: var(--bg-main);
    border: 1px solid var(--border-color);
}

.heatmap-cell.level-1 { background: #86EFAC; border-color: #4ADE80; }
.heatmap-cell.level-2 { background: #4ADE80; border-color: #22C55E; }
.heatmap-cell.level-3 { background: #16A34A; border-color: #15803D; }
.heatmap-cell.level-4 { background: #14532D; border-color: #14532D; }

.mastery-bar-track {
    width: 100%;
    height: 9px;
    background: var(--bg-main);
    border-radius: 999px;
    overflow: hidden;
    display: flex;
}

.mastery-seg.seg-mastered { background: var(--secondary); }
.mastery-seg.seg-learning { background: var(--warning); }
.mastery-seg.seg-unlearned { background: var(--border-color); }

/* CLS-Guarded AdSense Slot (#28) */
.ad-banner-slot {
    width: 100%;
    min-height: 90px;
    max-height: 110px;
    border-radius: var(--radius-md);
    border: 1px dashed var(--border-color);
    background: var(--bg-surface);
    display: flex;
    align-items: center;
    justify-content: center;
    overflow: hidden;
    padding: 0.5rem;
}

/* Printable 2-Column Exam Sheet (#15) */
.printable-sheet {
    display: none;
}

@media print {
    body {
        background: #ffffff !important;
        color: #000000 !important;
    }
    .app-header,
    .header-bar,
    .section-card,
    .days-grid,
    #modal-layer,
    #snackbar-layer,
    .ad-banner-slot {
        display: none !important;
    }
    .printable-sheet {
        display: block !important;
    }
    .print-2col-list {
        column-count: 2;
        column-gap: 24px;
        column-rule: 1px solid #ccc;
        margin-top: 1rem;
    }
    .print-item-row {
        break-inside: avoid;
        padding: 6px 0;
        border-bottom: 1px dotted #ccc;
        font-size: 10pt;
    }
}