:root {
    --primary: #1a73e8;
    --primary-dark: #1557b0;
    --success: #34a853;
    --danger: #ea4335;
    --warning: #fbbc04;
    --bg: #f8f9fa;
    --card-bg: #ffffff;
    --text: #202124;
    --text-secondary: #5f6368;
    --border: #dadce0;
    --radius: 12px;
    --shadow: 0 1px 3px rgba(0,0,0,0.12), 0 1px 2px rgba(0,0,0,0.08);
    --shadow-lg: 0 4px 12px rgba(0,0,0,0.15);
}

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

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
    background: var(--bg);
    color: var(--text);
    min-height: 100vh;
}

.navbar {
    background: var(--card-bg);
    border-bottom: 1px solid var(--border);
    padding: 0 24px;
    display: flex;
    align-items: center;
    height: 56px;
    position: sticky;
    top: 0;
    z-index: 100;
}

.nav-brand {
    font-size: 20px;
    font-weight: 700;
    color: var(--primary);
    text-decoration: none;
    margin-right: 32px;
}

.nav-links { display: flex; gap: 8px; }

.nav-link {
    color: var(--text-secondary);
    text-decoration: none;
    padding: 8px 16px;
    border-radius: 8px;
    font-size: 14px;
    font-weight: 500;
    transition: all 0.2s;
}

.nav-link:hover { background: #e8f0fe; color: var(--primary); }

.container {
    max-width: 960px;
    margin: 0 auto;
    padding: 24px 16px;
}

.hero {
    text-align: center;
    padding: 48px 0 32px;
}

.hero h1 { font-size: 40px; font-weight: 700; color: var(--primary); margin-bottom: 8px; }
.hero .subtitle { font-size: 18px; color: var(--text-secondary); }
.hero .stat-line { font-size: 14px; color: var(--text-secondary); margin-top: 8px; }

.mode-cards {
    display: grid;
    grid-template-columns: 1fr 1fr 1fr;
    gap: 20px;
    margin-bottom: 40px;
}

.config-section { margin-bottom: 32px; }
.config-block { margin-bottom: 24px; }
.config-block h2 { font-size: 20px; margin-bottom: 12px; }

.choice-grid {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}

.choice-btn {
    padding: 10px 20px;
    border: 2px solid var(--border);
    border-radius: 8px;
    background: var(--card-bg);
    cursor: pointer;
    transition: all 0.2s;
    display: inline-flex;
    align-items: center;
    gap: 10px;
    min-width: 140px;
    user-select: none;
}

.choice-btn:hover { border-color: var(--primary); }
.choice-btn.selected { border-color: var(--primary); background: #e8f0fe; }

.choice-btn input[type="checkbox"] {
    width: 18px;
    height: 18px;
    accent-color: var(--primary);
    flex-shrink: 0;
    pointer-events: none;
}

.choice-name { font-weight: 600; font-size: 14px; }
.choice-count { font-size: 12px; color: var(--text-secondary); }

.hint { font-size: 14px; font-weight: 400; color: var(--text-secondary); }

.card {
    background: var(--card-bg);
    border: 2px solid var(--border);
    border-radius: var(--radius);
    padding: 32px 24px;
    text-align: center;
    cursor: pointer;
    transition: all 0.2s;
}

.card:hover { border-color: var(--primary); box-shadow: var(--shadow-lg); transform: translateY(-2px); }
.card-danger { border-color: #f28b82; }
.card-danger:hover { border-color: var(--danger); }

.badge {
    display: inline-block;
    background: var(--danger);
    color: white;
    font-size: 12px;
    font-weight: 700;
    padding: 2px 8px;
    border-radius: 10px;
    vertical-align: middle;
    margin-left: 4px;
}

.btn-danger { background: var(--danger); color: white; }
.btn-danger:hover { background: #c5221f; }
.btn-small { font-size: 12px; padding: 4px 12px; }

.quiz-mode {
    font-weight: 700;
    color: var(--primary);
    padding: 2px 10px;
    background: #e8f0fe;
    border-radius: 6px;
    font-size: 13px;
}

.topic-info { display: flex; flex-direction: column; gap: 2px; }
.topic-wrong { color: var(--danger); font-weight: 600; }

.card-icon { font-size: 48px; margin-bottom: 12px; }
.card h2 { font-size: 22px; margin-bottom: 8px; }
.card p { font-size: 14px; color: var(--text-secondary); line-height: 1.5; }

.topics-section { margin-top: 16px; }
.topics-section h2 { font-size: 24px; margin-bottom: 8px; }
.section-desc { color: var(--text-secondary); margin-bottom: 16px; }

.topics-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 12px;
}

.topic-card {
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 16px 20px;
    cursor: pointer;
    display: flex;
    justify-content: space-between;
    align-items: center;
    transition: all 0.2s;
}

.topic-card:hover { border-color: var(--primary); background: #f0f7ff; }
.topic-card h3 { font-size: 15px; font-weight: 600; }
.topic-questions { font-size: 13px; color: var(--text-secondary); white-space: nowrap; }

.quiz-container { display: none; }
.quiz-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: 20px;
    padding: 16px 20px;
    background: var(--card-bg);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
}

.quiz-info { display: flex; gap: 24px; align-items: center; }
.quiz-info span { font-size: 14px; font-weight: 500; }
.quiz-timer { font-size: 18px; font-weight: 700; color: var(--primary); }
.quiz-timer.warning { color: var(--danger); }

.progress-bar {
    height: 4px;
    background: var(--border);
    border-radius: 2px;
    margin-bottom: 24px;
    overflow: hidden;
}

.progress-fill {
    height: 100%;
    background: var(--primary);
    border-radius: 2px;
    transition: width 0.3s;
}

.question-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 32px;
    box-shadow: var(--shadow);
    margin-bottom: 16px;
}

.question-topic {
    display: inline-block;
    font-size: 12px;
    font-weight: 600;
    color: var(--primary);
    background: #e8f0fe;
    padding: 4px 12px;
    border-radius: 20px;
    margin-bottom: 16px;
}

.question-number { font-size: 13px; color: var(--text-secondary); margin-bottom: 8px; }
.question-text { font-size: 18px; font-weight: 600; line-height: 1.5; margin-bottom: 24px; }

.options { display: flex; flex-direction: column; gap: 10px; }

.option-btn {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 14px 20px;
    border: 2px solid var(--border);
    border-radius: 10px;
    background: var(--card-bg);
    cursor: pointer;
    font-size: 15px;
    text-align: left;
    transition: all 0.2s;
    width: 100%;
}

.option-btn:hover { border-color: var(--primary); background: #f0f7ff; }
.option-btn.selected { border-color: var(--primary); background: #e8f0fe; }

.option-btn.correct {
    border-color: var(--success);
    background: #e6f4ea;
    color: #1e7e34;
}

.option-btn.wrong {
    border-color: var(--danger);
    background: #fce8e6;
    color: #c5221f;
}

.option-letter {
    width: 32px;
    height: 32px;
    border-radius: 50%;
    background: var(--bg);
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 14px;
    flex-shrink: 0;
}

.option-btn.correct .option-letter { background: var(--success); color: white; }
.option-btn.wrong .option-letter { background: var(--danger); color: white; }

.explanation {
    display: none;
    margin-top: 20px;
    padding: 16px 20px;
    background: #fff8e1;
    border-left: 4px solid var(--warning);
    border-radius: 0 8px 8px 0;
    font-size: 14px;
    line-height: 1.6;
}

.explanation.show { display: block; }

.quiz-actions {
    display: flex;
    justify-content: space-between;
    margin-top: 20px;
}

.btn {
    padding: 12px 24px;
    border: none;
    border-radius: 8px;
    font-size: 15px;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-primary { background: var(--primary); color: white; }
.btn-primary:hover { background: var(--primary-dark); }
.btn-primary:disabled { opacity: 0.5; cursor: not-allowed; }
.btn-secondary { background: var(--bg); color: var(--text); border: 1px solid var(--border); }
.btn-secondary:hover { background: #e8eaed; }

.results-container { display: none; }
.results-card {
    background: var(--card-bg);
    border-radius: var(--radius);
    padding: 40px;
    box-shadow: var(--shadow);
    text-align: center;
    margin-bottom: 24px;
}

.results-icon { font-size: 64px; margin-bottom: 16px; }
.results-title { font-size: 28px; font-weight: 700; margin-bottom: 8px; }
.results-subtitle { font-size: 16px; color: var(--text-secondary); margin-bottom: 24px; }

.results-score {
    font-size: 48px;
    font-weight: 700;
    margin-bottom: 8px;
}

.results-score.pass { color: var(--success); }
.results-score.fail { color: var(--danger); }

.results-detail { font-size: 16px; color: var(--text-secondary); margin-bottom: 24px; }

.topic-results {
    text-align: left;
    margin-top: 24px;
    padding-top: 24px;
    border-top: 1px solid var(--border);
}

.topic-result {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 8px 0;
}

.topic-result-name { font-size: 14px; }
.topic-result-score { font-size: 14px; font-weight: 600; }
.topic-result-bar {
    height: 6px;
    background: var(--border);
    border-radius: 3px;
    width: 120px;
    margin: 0 12px;
}

.topic-result-bar-fill {
    height: 100%;
    border-radius: 3px;
    transition: width 0.5s;
}

.results-actions { display: flex; gap: 12px; justify-content: center; flex-wrap: wrap; }

#ref-search { margin-bottom: 24px; }
#ref-search input {
    width: 100%;
    padding: 12px 16px;
    border: 2px solid var(--border);
    border-radius: 8px;
    font-size: 15px;
    outline: none;
    transition: border-color 0.2s;
}
#ref-search input:focus { border-color: var(--primary); }

.ref-group { margin-bottom: 24px; }
.ref-group-title {
    font-size: 18px;
    font-weight: 700;
    padding: 12px 16px;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: 8px 8px 0 0;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 8px;
    user-select: none;
}
.ref-group-title:hover { background: #f0f7ff; }
.ref-count { font-size: 13px; font-weight: 400; color: var(--text-secondary); }
.ref-toggle { margin-left: auto; font-size: 14px; color: var(--text-secondary); }

.ref-table {
    width: 100%;
    border-collapse: collapse;
    border: 1px solid var(--border);
    border-top: none;
    border-radius: 0 0 8px 8px;
    background: var(--card-bg);
}
.ref-table th {
    text-align: left;
    padding: 10px 16px;
    background: #f8f9fa;
    font-size: 13px;
    font-weight: 600;
    color: var(--text-secondary);
    border-bottom: 1px solid var(--border);
}
.ref-table td {
    padding: 10px 16px;
    font-size: 14px;
    border-bottom: 1px solid #f0f0f0;
    vertical-align: top;
    line-height: 1.5;
}
.ref-table tr:last-child td { border-bottom: none; }
.ref-q { width: 45%; }
.ref-a { width: 20%; font-weight: 600; color: var(--success); }
.ref-e { width: 35%; color: #666; font-size: 0.9em; }

.question-image {
    text-align: center;
    margin: 12px 0;
}
.question-image img {
    max-width: 100%;
    max-height: 300px;
    border-radius: 8px;
    cursor: pointer;
    transition: transform 0.2s;
}
.question-image img.zoomed {
    transform: scale(1.8);
    z-index: 100;
    position: relative;
}

@media (max-width: 640px) {
    .mode-cards { grid-template-columns: 1fr; }
    .hero h1 { font-size: 28px; }
    .question-card { padding: 20px; }
    .quiz-header { flex-direction: column; gap: 8px; }
    .results-actions { flex-direction: column; }
    .choice-grid { flex-direction: column; }
    .analytics-table th:nth-child(2), .analytics-table td:nth-child(2),
    .analytics-table th:nth-child(3), .analytics-table td:nth-child(3) { display: none; }
}

.analytics-summary {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 16px;
    margin: 20px 0;
}
.analytics-card {
    background: var(--card-bg);
    border-radius: 12px;
    padding: 20px;
    text-align: center;
    box-shadow: 0 1px 3px rgba(0,0,0,0.08);
}
.analytics-card-danger { border: 2px solid var(--danger); }
.analytics-num { font-size: 32px; font-weight: 700; color: var(--text); }
.analytics-card-danger .analytics-num { color: var(--danger); }
.analytics-label { font-size: 14px; color: var(--text-secondary); margin-top: 4px; }
.analytics-section-title {
    font-size: 18px;
    margin: 28px 0 12px;
    color: var(--text);
}
.analytics-table-wrap { overflow-x: auto; }
.analytics-table {
    width: 100%;
    border-collapse: collapse;
    background: var(--card-bg);
    border-radius: 12px;
    overflow: hidden;
    box-shadow: 0 1px 3px rgba(0,0,0,0.08);
}
.analytics-table th {
    background: var(--primary);
    color: #fff;
    padding: 12px 16px;
    text-align: left;
    font-size: 13px;
    font-weight: 600;
    white-space: nowrap;
}
.analytics-table td {
    padding: 12px 16px;
    border-bottom: 1px solid #e8e8e8;
    font-size: 14px;
}
.analytics-table tbody tr { cursor: pointer; transition: background 0.15s; }
.analytics-table tbody tr:hover { background: #f0f4ff; }
.analytics-table tbody tr:last-child td { border-bottom: none; }
.analytics-topic { font-weight: 500; }
.topic-section {
    display: inline-block;
    background: var(--primary);
    color: #fff;
    font-size: 11px;
    padding: 2px 8px;
    border-radius: 4px;
    margin-right: 6px;
    font-weight: 600;
}
.analytics-wrong { color: var(--danger); font-weight: 600; }
.analytics-bar {
    display: flex;
    align-items: center;
    gap: 8px;
    min-width: 120px;
}
.analytics-bar-fill {
    height: 8px;
    border-radius: 4px;
    flex: 1;
    min-width: 40px;
}
.analytics-pct { font-size: 13px; font-weight: 600; white-space: nowrap; }
.analytics-level {
    display: inline-block;
    font-size: 12px;
    padding: 3px 10px;
    border-radius: 12px;
    font-weight: 600;
}
.level-easy { background: #e6f4ea; color: #1e7e34; }
.level-mid { background: #fff3e0; color: #e65100; }
.level-hard { background: #fce4ec; color: #c62828; }
.analytics-notstarted {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
}
.analytics-tag {
    background: var(--card-bg);
    border: 1px solid #ddd;
    border-radius: 8px;
    padding: 8px 14px;
    font-size: 13px;
    cursor: pointer;
    transition: border-color 0.15s;
}
.analytics-tag:hover { border-color: var(--primary); }

.nav-profile {
    margin-left: auto;
    position: relative;
}
.profile-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 12px;
    border-radius: 20px;
    background: #e8f0fe;
    cursor: pointer;
    transition: background 0.2s;
    white-space: nowrap;
}
.profile-btn:hover { background: #d2e3fc; }
.profile-icon { font-size: 18px; }
.profile-name { font-size: 13px; font-weight: 500; color: var(--primary); max-width: 120px; overflow: hidden; text-overflow: ellipsis; }
.profile-arrow { font-size: 10px; color: var(--primary); }
.profile-menu {
    position: absolute;
    top: 44px;
    right: 0;
    background: var(--card-bg);
    border: 1px solid var(--border);
    border-radius: var(--radius);
    box-shadow: var(--shadow-lg);
    min-width: 220px;
    z-index: 200;
    padding: 8px;
}
.profile-menu.hidden { display: none; }
.profile-user-item {
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 8px 10px;
    border-radius: 8px;
    cursor: pointer;
    transition: background 0.15s;
}
.profile-user-item:hover { background: #f1f3f4; }
.profile-user-item.active { background: #e8f0fe; }
.profile-user-item.active .profile-user-name { font-weight: 600; color: var(--primary); }
.profile-user-name { flex: 1; font-size: 14px; }
.profile-delete-btn {
    background: none;
    border: none;
    color: var(--text-secondary);
    font-size: 16px;
    cursor: pointer;
    padding: 0 4px;
    line-height: 1;
    border-radius: 4px;
}
.profile-delete-btn:hover { color: var(--danger); background: #fce8e6; }
.profile-divider { height: 1px; background: var(--border); margin: 6px 0; }
.profile-new { display: flex; gap: 6px; padding: 4px 0; }
.profile-new input {
    flex: 1;
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 6px 10px;
    font-size: 13px;
    outline: none;
}
.profile-new input:focus { border-color: var(--primary); }
.profile-empty { font-size: 13px; color: var(--text-secondary); padding: 8px 4px; text-align: center; }