:root {
    --bg: #0f1419;
    --bg-elevated: #1a2332;
    --bg-card: #243044;
    --border: #3d4f66;
    --text: #eef2f7;
    --text-muted: #a8b5c6;
    --accent: #2dc8b4;
    --accent-hover: #3dd9c4;
    --success: #3dba6a;
    --danger: #e85d5d;
    --warning: #e8b84a;
    --radius: 12px;
    --shadow: 0 8px 32px rgba(0, 0, 0, 0.35);
    --font: 'Segoe UI', system-ui, -apple-system, sans-serif;
}

[data-theme="light"] {
    --bg: #f0f4f8;
    --bg-elevated: #ffffff;
    --bg-card: #ffffff;
    --border: #c5d0de;
    --text: #1a2332;
    --text-muted: #5a6b7d;
    --shadow: 0 4px 20px rgba(26, 35, 50, 0.08);
}

*, *::before, *::after { box-sizing: border-box; }

html { font-size: 16px; }

body {
    margin: 0;
    min-height: 100vh;
    font-family: var(--font);
    background: var(--bg);
    color: var(--text);
    line-height: 1.5;
}

a { color: var(--accent); }

.app-header {
    position: sticky;
    top: 0;
    z-index: 100;
    display: flex;
    flex-wrap: wrap;
    align-items: center;
    gap: 0.75rem;
    padding: 0.75rem 1.25rem;
    background: var(--bg-elevated);
    border-bottom: 1px solid var(--border);
}

.app-brand {
    font-weight: 700;
    font-size: 1.1rem;
    color: var(--text);
    text-decoration: none;
    margin-right: auto;
}

.app-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 0.35rem;
}

.app-nav a, .app-nav button.nav-btn {
    padding: 0.45rem 0.75rem;
    border-radius: 8px;
    text-decoration: none;
    color: var(--text-muted);
    background: transparent;
    border: none;
    font: inherit;
    cursor: pointer;
}

.app-nav a:hover, .app-nav a.active, .app-nav button.nav-btn:hover {
    color: var(--text);
    background: rgba(45, 200, 180, 0.12);
}

.app-nav a.active { color: var(--accent); font-weight: 600; }

.app-main {
    max-width: 920px;
    margin: 0 auto;
    padding: 1.5rem 1.25rem 3rem;
}

.page-title {
    margin: 0 0 0.35rem;
    font-size: 1.75rem;
    font-weight: 700;
    color: var(--text);
}

.page-lead {
    margin: 0 0 1.5rem;
    color: var(--text-muted);
}

.card {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1.25rem;
    margin-bottom: 1rem;
    box-shadow: var(--shadow);
    color: var(--text);
}

.card h2, .card h3 {
    margin: 0 0 0.75rem;
    color: var(--text);
}

.stat-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(130px, 1fr));
    gap: 0.75rem;
    margin-bottom: 1.5rem;
}

.stat-box {
    background: var(--bg-card);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    padding: 1rem;
    text-align: center;
}

.stat-box .value {
    display: block;
    font-size: 2rem;
    font-weight: 700;
    color: var(--accent);
    line-height: 1.1;
}

.stat-box .label {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: 0.25rem;
}

.btn-row {
    display: flex;
    flex-wrap: wrap;
    gap: 0.6rem;
    margin: 1rem 0;
}

.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 0.4rem;
    min-height: 44px;
    padding: 0.6rem 1.1rem;
    border: none;
    border-radius: 10px;
    font: inherit;
    font-weight: 600;
    cursor: pointer;
    text-decoration: none;
    transition: background 0.15s, transform 0.1s;
}

.btn:active { transform: scale(0.98); }

.btn-primary {
    background: var(--accent);
    color: #0a1218;
}

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

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

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

.btn-success {
    background: var(--success);
    color: #fff;
    width: 100%;
    font-size: 1rem;
    padding: 1rem;
}

.btn-danger {
    background: var(--danger);
    color: #fff;
    width: 100%;
    font-size: 1rem;
    padding: 1rem;
}

.chips {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
    margin-bottom: 1rem;
}

.chip {
    padding: 0.25rem 0.65rem;
    border-radius: 999px;
    font-size: 0.78rem;
    background: rgba(45, 200, 180, 0.15);
    color: var(--accent);
    border: 1px solid rgba(45, 200, 180, 0.3);
}

.chip.mandatory { background: rgba(232, 93, 93, 0.15); color: #f08080; border-color: rgba(232, 93, 93, 0.35); }

.learn-question {
    font-size: 1.35rem;
    font-weight: 600;
    line-height: 1.45;
    margin: 0 0 1.5rem;
    color: var(--text);
}

.learn-answer {
    margin-top: 1.25rem;
    padding-top: 1.25rem;
    border-top: 1px solid var(--border);
}

.learn-answer h3 {
    margin: 0 0 0.5rem;
    font-size: 0.85rem;
    text-transform: uppercase;
    letter-spacing: 0.05em;
    color: var(--accent);
}

.learn-explanation {
    margin-top: 0.75rem;
    font-style: italic;
    color: var(--text-muted);
}

.answer-actions {
    display: grid;
    gap: 0.75rem;
    margin-top: 1.5rem;
}

.keyboard-hint {
    text-align: center;
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-top: 1rem;
}

.form-grid {
    display: grid;
    gap: 0.75rem;
}

.form-grid label {
    display: flex;
    flex-direction: column;
    gap: 0.3rem;
    font-size: 0.85rem;
    color: var(--text-muted);
}

.form-grid input, .form-grid select, .form-grid textarea {
    padding: 0.55rem 0.75rem;
    border-radius: 8px;
    border: 1px solid var(--border);
    background: var(--bg-elevated);
    color: var(--text);
    font: inherit;
}

.form-grid input:focus, .form-grid select:focus, .form-grid textarea:focus {
    outline: 2px solid var(--accent);
    outline-offset: 1px;
}

.filters {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(160px, 1fr));
    gap: 0.75rem;
    margin-bottom: 1rem;
}

.card-list-item {
    margin-bottom: 0.75rem;
}

.card-list-item .meta {
    font-size: 0.8rem;
    color: var(--text-muted);
    margin-bottom: 0.35rem;
}

.card-list-item .question-preview {
    font-weight: 600;
    margin-bottom: 0.5rem;
}

.card-list-item .actions {
    display: flex;
    flex-wrap: wrap;
    gap: 0.4rem;
}

.card-list-item .actions button {
    padding: 0.35rem 0.65rem;
    font-size: 0.82rem;
    min-height: auto;
}

.bar-chart {
    display: flex;
    min-height: 2.5rem;
    border-radius: 8px;
    overflow: hidden;
    margin: 0.75rem 0;
}

.bar-known { flex: 1; background: var(--success); display: flex; align-items: center; justify-content: center; color: #fff; font-size: 0.85rem; }
.bar-unknown { flex: 1; background: var(--danger); display: flex; align-items: center; justify-content: center; color: #fff; font-size: 0.85rem; }
.bar-q75 { flex: 1; background: #4caf7a; display: flex; align-items: center; justify-content: center; color: #fff; font-size: 0.8rem; }
.bar-q50 { flex: 1; background: var(--warning); display: flex; align-items: center; justify-content: center; color: #1a2332; font-size: 0.8rem; }
.bar-q25 { flex: 1; background: #e0894a; display: flex; align-items: center; justify-content: center; color: #fff; font-size: 0.8rem; }

.quality-bar { min-height: 2.75rem; }
.quality-actions { grid-template-columns: 1fr; }

.btn-q75 { background: #4caf7a; color: #fff; width: 100%; font-size: 1rem; padding: 0.85rem; }
.btn-q50 { background: var(--warning); color: #1a2332; width: 100%; font-size: 1rem; padding: 0.85rem; }
.btn-q25 { background: #e0894a; color: #fff; width: 100%; font-size: 1rem; padding: 0.85rem; }

@media (min-width: 720px) {
    .quality-actions { grid-template-columns: 1fr 1fr; }
    .quality-actions .btn-success,
    .quality-actions .btn-danger { grid-column: 1 / -1; }
}

.heatmap {
    display: grid;
    grid-template-columns: repeat(53, 1fr);
    gap: 2px;
    margin-top: 0.75rem;
}

.heat-cell {
    aspect-ratio: 1;
    border-radius: 2px;
    background: var(--bg-elevated);
}

.heat-cell.l1 { background: rgba(45, 200, 180, 0.25); }
.heat-cell.l2 { background: rgba(45, 200, 180, 0.45); }
.heat-cell.l3 { background: rgba(45, 200, 180, 0.65); }
.heat-cell.l4 { background: var(--accent); }

.hidden { display: none !important; }

.app-footer {
    text-align: center;
    padding: 1.5rem;
    font-size: 0.8rem;
    color: var(--text-muted);
    border-top: 1px solid var(--border);
}

@media (max-width: 640px) {
    .app-nav { width: 100%; }
    .app-nav a, .app-nav button.nav-btn { flex: 1; text-align: center; font-size: 0.85rem; padding: 0.4rem; }
}