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

:root {
    --tg-theme-bg-color: #18181b;
    --tg-theme-text-color: #f4f4f5;
    --tg-theme-hint-color: #a1a1aa;
    --tg-theme-link-color: #60a5fa;
    --tg-theme-button-color: #3b82f6;
    --tg-theme-button-text-color: #ffffff;
    --tg-theme-secondary-bg-color: #27272a;
}

body {
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Helvetica, Arial, sans-serif;
    background-color: var(--tg-theme-bg-color);
    color: var(--tg-theme-text-color);
    line-height: 1.6;
    padding: 0;
    margin: 0;
    /* iOS safe area (notch / home indicator) */
    padding-top: env(safe-area-inset-top);
    padding-bottom: env(safe-area-inset-bottom);
    padding-left: env(safe-area-inset-left);
    padding-right: env(safe-area-inset-right);
}

#app {
    max-width: 480px;
    margin: 0 auto;
    padding: 0;
    min-height: 100vh;
    background: var(--tg-theme-bg-color);
}

@media (min-width: 600px) {
    body {
        background: #0f0f11;
    }
    #app {
        box-shadow: 0 0 40px rgba(0,0,0,0.6);
        border-left: 1px solid rgba(255,255,255,0.06);
        border-right: 1px solid rgba(255,255,255,0.06);
    }
}

.app-header {
    background: linear-gradient(135deg, var(--tg-theme-button-color) 0%, #2b7de9 100%);
    color: white;
    padding: 10px 20px;
    text-align: center;
    box-shadow: 0 2px 10px rgba(0,0,0,0.1);
}

.app-header h1 {
    font-size: 20px;
    margin-bottom: 2px;
}

.subtitle {
    font-size: 14px;
    opacity: 0.9;
}

.main-content {
    padding: 15px;
}

.card {
    background-color: var(--tg-theme-secondary-bg-color);
    border-radius: 12px;
    padding: 20px;
    margin-bottom: 15px;
    box-shadow: 0 2px 8px rgba(0,0,0,0.05);
}

.card h2 {
    font-size: 18px;
    margin-bottom: 15px;
    color: var(--tg-theme-text-color);
}

.info-text {
    color: var(--tg-theme-hint-color);
    font-size: 14px;
}

/* Progress Bar */
.progress-bar {
    width: 100%;
    height: 6px;
    background-color: rgba(255,255,255,0.1);
    border-radius: 10px;
    overflow: hidden;
    margin-bottom: 10px;
}

.progress-fill {
    height: 100%;
    background: linear-gradient(90deg, #4CAF50 0%, #8BC34A 100%);
    width: 0%;
    transition: width 0.3s ease;
}

.progress-text {
    text-align: center;
    font-size: 14px;
    color: var(--tg-theme-hint-color);
}

/* Book Content */
.book-content {
    background-color: var(--tg-theme-secondary-bg-color);
    padding: 20px;
    border-radius: 8px;
    margin: 15px 0;
    min-height: 300px;
    line-height: 1.8;
    font-size: 16px;
    white-space: pre-wrap;
    word-wrap: break-word;
}

/* Navigation */
.navigation-buttons {
    display: flex;
    justify-content: space-between;
    align-items: center;
    gap: 10px;
    margin: 10px 0;
}

.nav-button {
    flex: 1;
    padding: 12px 20px;
    background-color: var(--tg-theme-button-color);
    color: var(--tg-theme-button-text-color);
    border: none;
    border-radius: 8px;
    font-size: 14px;
    cursor: pointer;
    transition: opacity 0.2s;
}

.nav-button:hover:not(:disabled) {
    opacity: 0.9;
}

.nav-button:disabled {
    opacity: 0.4;
    cursor: not-allowed;
}

.page-info {
    font-size: 14px;
    color: var(--tg-theme-hint-color);
    white-space: nowrap;
}

/* Action Buttons */
.action-button {
    width: 100%;
    padding: 12px;
    background-color: var(--tg-theme-button-color);
    color: var(--tg-theme-button-text-color);
    border: none;
    border-radius: 8px;
    font-size: 14px;
    cursor: pointer;
    transition: opacity 0.2s;
    margin-bottom: 10px;
}

.action-button:hover {
    opacity: 0.9;
}

/* Bookmarks */
.bookmarks-list {
    margin-top: 15px;
}

.bookmark-item {
    background-color: var(--tg-theme-secondary-bg-color);
    padding: 12px;
    border-radius: 8px;
    margin-bottom: 8px;
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.bookmark-info {
    flex: 1;
}

.bookmark-page {
    font-weight: bold;
    color: var(--tg-theme-link-color);
}

.bookmark-note {
    font-size: 13px;
    color: var(--tg-theme-hint-color);
    margin-top: 4px;
}

.delete-button {
    padding: 6px 12px;
    background-color: #f44336;
    color: white;
    border: none;
    border-radius: 6px;
    font-size: 12px;
    cursor: pointer;
}

/* Vocabulary */
.vocab-input-group {
    display: flex;
    flex-direction: column;
    gap: 10px;
    margin-bottom: 15px;
}

.button-group {
    display: flex;
    gap: 8px;
}

.ai-button-small {
    flex: 1;
    padding: 8px 12px;
    background-color: #9C27B0;
    color: white;
    border: none;
    border-radius: 6px;
    font-size: 12px;
    cursor: pointer;
    transition: opacity 0.2s;
}

.ai-button-small:hover:not(:disabled) {
    opacity: 0.9;
}

.ai-button-small:disabled {
    opacity: 0.5;
    cursor: not-allowed;
}

.input-field {
    width: 100%;
    padding: 12px;
    border: 1px solid #ddd;
    border-radius: 8px;
    font-size: 14px;
    background-color: var(--tg-theme-secondary-bg-color);
}

.vocab-list {
    margin-top: 15px;
}

.vocab-item {
    background-color: var(--tg-theme-secondary-bg-color);
    padding: 12px;
    border-radius: 8px;
    margin-bottom: 8px;
}

.vocab-word {
    font-weight: bold;
    color: var(--tg-theme-text-color);
    font-size: 16px;
}

.vocab-definition {
    color: var(--tg-theme-hint-color);
    font-size: 14px;
    margin-top: 4px;
}

/* Grammar Feedback */
.grammar-feedback {
    background-color: #fff3cd;
    border: 1px solid #ffc107;
    border-radius: 8px;
    padding: 12px;
    margin: 10px 0;
    font-size: 13px;
    line-height: 1.6;
}

/* AI Actions */
.ai-actions {
    display: flex;
    justify-content: center;
    margin: 15px 0;
}

.ai-button {
    padding: 12px 24px;
    background-color: #9C27B0;
    color: white;
    border: none;
    border-radius: 8px;
    font-size: 14px;
    cursor: pointer;
    transition: opacity 0.2s;
}

.ai-button:hover:not(:disabled) {
    opacity: 0.9;
}

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

/* Summary Section */
.summary-section {
    background-color: #e8f5e9;
    border: 1px solid #4CAF50;
    border-radius: 8px;
    padding: 15px;
    margin: 15px 0;
}

.summary-section h3 {
    font-size: 16px;
    margin-bottom: 10px;
    color: #2e7d32;
}

.summary-content {
    font-size: 14px;
    line-height: 1.6;
}

.summary-content ul {
    margin-top: 10px;
    padding-left: 20px;
}

.summary-content li {
    margin-bottom: 5px;
}

/* Chatbot */
.chat-messages {
    background-color: var(--tg-theme-secondary-bg-color);
    border-radius: 8px;
    padding: 15px;
    max-height: 400px;
    overflow-y: auto;
    margin-bottom: 15px;
}

.chat-message {
    padding: 10px 15px;
    border-radius: 12px;
    margin-bottom: 10px;
    max-width: 85%;
    word-wrap: break-word;
}

.user-message {
    background-color: var(--tg-theme-button-color);
    color: var(--tg-theme-button-text-color);
    margin-left: auto;
    text-align: right;
}

.bot-message {
    background-color: var(--tg-theme-secondary-bg-color);
    color: var(--tg-theme-text-color);
    margin-right: auto;
}

.loading-message {
    opacity: 0.7;
}

.chat-input-group {
    display: flex;
    gap: 10px;
}

.chat-input-group .input-field {
    flex: 1;
}

.chat-input-group .action-button {
    width: auto;
    min-width: 80px;
    margin-bottom: 0;
}

/* Footer */
.app-footer {
    text-align: center;
    padding: 20px;
    color: var(--tg-theme-hint-color);
    font-size: 12px;
}

/* Responsive Design */
@media (max-width: 480px) {
    .app-header h1 {
        font-size: 24px;
    }
    
    .book-content {
        font-size: 15px;
        padding: 15px;
    }
    
    .card {
        padding: 15px;
    }
}

/* ── Screen management ───────────────────────────────────────────────────── */
.screen { display: none; }
.screen.active { display: block; }

/* ── Mode tabs ───────────────────────────────────────────────────────────── */
.mode-tabs {
    display: flex;
    background: var(--tg-theme-secondary-bg-color);
    border-bottom: 1px solid rgba(0,0,0,0.08);
    position: sticky;
    top: 0;
    z-index: 100;
}
.mode-tab {
    flex: 1;
    padding: 12px 8px;
    border: none;
    background: transparent;
    color: var(--tg-theme-hint-color);
    font-size: 15px;
    cursor: pointer;
    transition: color 0.2s;
    border-bottom: 2px solid transparent;
}
.mode-tab.active {
    color: var(--tg-theme-button-color);
    border-bottom-color: var(--tg-theme-button-color);
    font-weight: 600;
}

/* ── Quest stats bar ─────────────────────────────────────────────────────── */
.quest-stats-bar {
    display: flex;
    justify-content: space-around;
    padding: 14px 15px 10px;
    background: linear-gradient(135deg, #1e293b 0%, #1e1e2e 100%);
    border-bottom: 1px solid rgba(255,255,255,0.07);
    margin-bottom: 4px;
}
.quest-stat { text-align: center; }
.quest-stat-label {
    display: block;
    font-size: 11px;
    color: var(--tg-theme-hint-color);
    text-transform: uppercase;
    letter-spacing: 0.5px;
}
.quest-stat-value {
    font-size: 20px;
    font-weight: 700;
    color: var(--tg-theme-text-color);
}

/* ── Levels grid ─────────────────────────────────────────────────────────── */
.levels-grid {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 8px;
    padding: 0 15px 10px;
}
.level-card {
    background: var(--tg-theme-secondary-bg-color);
    border-radius: 10px;
    padding: 10px 6px;
    text-align: center;
    cursor: pointer;
    transition: transform 0.12s, box-shadow 0.12s;
    border: 1px solid rgba(255,255,255,0.08);
    user-select: none;
    box-shadow: 0 2px 6px rgba(0,0,0,0.25);
}
.level-card:hover { transform: translateY(-2px); box-shadow: 0 4px 12px rgba(59,130,246,0.3); border-color: rgba(59,130,246,0.4); }
.level-card:active { transform: scale(0.93); }
.level-card.completed { border-color: #10b981; box-shadow: 0 2px 8px rgba(16,185,129,0.25); }
.level-card.locked { opacity: 0.4; cursor: not-allowed; }
.level-card .level-number {
    font-size: 20px;
    font-weight: 700;
    color: var(--tg-theme-button-color);
}
.level-card .level-status { font-size: 14px; color: var(--tg-theme-hint-color); margin-top: 2px; }
.level-card.completed .level-status { color: #10b981; }
.level-card .level-score { font-size: 10px; color: var(--tg-theme-hint-color); margin-top: 2px; }

/* ── Quest level nav bar ─────────────────────────────────────────────────── */
.level-nav-bar {
    background: var(--tg-theme-secondary-bg-color);
    padding: 12px 15px;
    display: flex;
    justify-content: space-between;
    align-items: center;
    flex-wrap: wrap;
    gap: 4px;
    position: sticky;
    top: 0;
    z-index: 50;
}
.level-title { font-size: 16px; font-weight: 700; color: var(--tg-theme-text-color); margin: 0; }
.level-score-info { font-size: 13px; color: var(--tg-theme-hint-color); }

/* ── Quiz container & question elements ──────────────────────────────────── */
.quiz-container { padding: 15px; min-height: 200px; }
.question-header { margin-bottom: 14px; }
.question-type {
    display: inline-block;
    background: var(--tg-theme-button-color);
    color: var(--tg-theme-button-text-color);
    padding: 3px 10px;
    border-radius: 12px;
    font-size: 12px;
    text-transform: capitalize;
    margin-bottom: 8px;
}
.question-text { font-size: 16px; font-weight: 600; color: var(--tg-theme-text-color); margin-bottom: 6px; }
.question-instruction { font-size: 13px; color: var(--tg-theme-hint-color); font-style: italic; margin: 0; }
.reading-passage {
    background: var(--tg-theme-secondary-bg-color);
    border-radius: 10px;
    padding: 12px;
    margin-bottom: 14px;
}
.passage-title { font-weight: 600; font-size: 14px; color: var(--tg-theme-button-color); margin-bottom: 6px; }
.passage-text { font-size: 14px; color: var(--tg-theme-text-color); line-height: 1.5; margin: 0; }
.sentence-with-blank {
    font-size: 15px;
    color: var(--tg-theme-text-color);
    padding: 10px 12px;
    background: var(--tg-theme-secondary-bg-color);
    border-radius: 8px;
    margin-bottom: 14px;
}
.answer-options { display: flex; flex-direction: column; gap: 8px; }
.answer-option {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 12px;
    background: var(--tg-theme-secondary-bg-color);
    border-radius: 10px;
    cursor: pointer;
    border: 2px solid transparent;
    transition: border-color 0.15s;
}
.answer-option.selected { border-color: var(--tg-theme-button-color); }
.answer-option.correct { border-color: #10b981; background: rgba(16,185,129,0.12); }
.answer-option.wrong { border-color: #ef4444; background: rgba(239,68,68,0.12); }
.option-marker {
    width: 28px; height: 28px; border-radius: 50%;
    background: var(--tg-theme-button-color); color: var(--tg-theme-button-text-color);
    display: flex; align-items: center; justify-content: center;
    font-weight: 700; font-size: 13px; flex-shrink: 0;
}
.option-text { font-size: 14px; color: var(--tg-theme-text-color); }
.blank-input {
    background: var(--tg-theme-secondary-bg-color);
    border: 2px solid var(--tg-theme-button-color);
    color: var(--tg-theme-text-color);
    border-radius: 8px; padding: 8px 12px; font-size: 15px;
    width: 160px; outline: none;
}
.feedback { margin-top: 12px; font-size: 13px; }

/* ── Quiz navigation bar ─────────────────────────────────────────────────── */
.quiz-navigation {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 12px 15px;
    background: var(--tg-theme-secondary-bg-color);
    border-top: 1px solid rgba(0,0,0,0.06);
    position: sticky;
    bottom: env(safe-area-inset-bottom, 0);
}
.nav-btn {
    padding: 10px 18px;
    border: 1px solid var(--tg-theme-hint-color);
    border-radius: 8px;
    font-size: 14px;
    font-weight: 600;
    cursor: pointer;
    background: transparent;
    color: var(--tg-theme-text-color);
    transition: opacity 0.2s;
}
.nav-btn.primary {
    background: var(--tg-theme-button-color);
    color: var(--tg-theme-button-text-color);
    border-color: var(--tg-theme-button-color);
}
.nav-btn.success { background: #10b981; color: #fff; border-color: #10b981; }
.nav-btn:disabled { opacity: 0.4; cursor: not-allowed; }

/* ── Results screen ──────────────────────────────────────────────────────── */
.results-screen { text-align: center; padding: 24px 16px; }
.results-score { font-size: 48px; font-weight: 700; color: var(--tg-theme-button-color); margin-bottom: 8px; }
.results-message { font-size: 20px; font-weight: 600; color: var(--tg-theme-text-color); margin-bottom: 20px; }
.results-stats { display: flex; justify-content: center; gap: 16px; margin-bottom: 24px; flex-wrap: wrap; }
.stat-box {
    background: var(--tg-theme-secondary-bg-color);
    border-radius: 12px; padding: 12px 16px; min-width: 80px;
}
.stat-box .stat-label {
    display: block; font-size: 11px; color: var(--tg-theme-hint-color);
    text-transform: uppercase; margin-bottom: 4px;
}
.stat-box .stat-value { font-size: 22px; font-weight: 700; color: var(--tg-theme-text-color); }
.results-actions {
    display: flex; flex-direction: column; gap: 10px;
    max-width: 280px; margin: 0 auto;
}