:root {
    --bg-primary: #0f172a;
    --bg-secondary: #1e293b;
    --bg-card: rgba(30, 41, 59, 0.7);
    --bg-card-hover: rgba(51, 65, 85, 0.8);
    --accent-red: #ef4444;
    --accent-gold: #f59e0b;
    --accent-primary: #6366f1;
    --accent-primary-hover: #4f46e5;
    --accent-gradient: linear-gradient(135deg, #ef4444 0%, #f59e0b 100%);
    --text-primary: #f8fafc;
    --text-secondary: #94a3b8;
    --text-muted: #64748b;
    --border-color: rgba(255, 255, 255, 0.08);
    --border-active: rgba(239, 68, 68, 0.5);
    --bubble-ai: #1e293b;
    --bubble-user: #4f46e5;
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.2);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.35);
    --shadow-glow: 0 0 20px rgba(239, 68, 68, 0.25);
    --radius-sm: 8px;
    --radius-md: 14px;
    --radius-lg: 20px;
}

body.light-theme {
    --bg-primary: #f1f5f9;
    --bg-secondary: #ffffff;
    --bg-card: rgba(255, 255, 255, 0.85);
    --bg-card-hover: rgba(241, 245, 249, 0.95);
    --text-primary: #0f172a;
    --text-secondary: #475569;
    --text-muted: #94a3b8;
    --border-color: rgba(0, 0, 0, 0.08);
    --bubble-ai: #ffffff;
    --bubble-user: #4f46e5;
    --shadow-sm: 0 2px 8px rgba(0, 0, 0, 0.05);
    --shadow-md: 0 8px 24px rgba(0, 0, 0, 0.08);
}

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

body {
    font-family: 'Plus Jakarta Sans', sans-serif;
    background-color: var(--bg-primary);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    transition: background-color 0.3s ease, color 0.3s ease;
}

.chinese-text {
    font-family: 'Noto Sans SC', sans-serif;
}

/* App Container */
.app-container {
    display: flex;
    height: 100vh;
    width: 100vw;
    overflow: hidden;
}

/* Sidebar */
.sidebar {
    width: 290px;
    background-color: var(--bg-secondary);
    border-right: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    padding: 24px 16px;
    flex-shrink: 0;
}

.brand {
    display: flex;
    align-items: center;
    gap: 14px;
    padding-bottom: 24px;
    border-bottom: 1px solid var(--border-color);
    margin-bottom: 20px;
}

.logo-icon {
    font-size: 24px;
    display: flex;
    gap: 2px;
    background: rgba(255, 255, 255, 0.05);
    padding: 8px 10px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
}

.brand-text h2 {
    font-size: 1.15rem;
    font-weight: 700;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.sub-brand {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.nav-menu {
    display: flex;
    flex-direction: column;
    gap: 8px;
    flex: 1;
    overflow-y: auto;
}

.nav-item {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 16px;
    border-radius: var(--radius-md);
    border: 1px solid transparent;
    background: transparent;
    color: var(--text-secondary);
    font-size: 0.92rem;
    font-weight: 600;
    cursor: pointer;
    text-align: left;
    transition: all 0.2s ease;
}

.nav-item i {
    font-size: 1.1rem;
    width: 20px;
}

.nav-item:hover {
    background: var(--bg-card);
    color: var(--text-primary);
    transform: translateX(4px);
}

.nav-item.active {
    background: var(--accent-gradient);
    color: #ffffff;
    box-shadow: var(--shadow-glow);
}

.nav-item.active i {
    color: #ffffff;
}

.sidebar-footer {
    padding-top: 16px;
    border-top: 1px solid var(--border-color);
    display: flex;
    flex-direction: column;
    gap: 10px;
}

.status-box {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 0.8rem;
    color: var(--text-muted);
    padding: 6px 12px;
    background: rgba(0, 0, 0, 0.15);
    border-radius: var(--radius-sm);
}

.status-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    background-color: #10b981;
}

.status-dot.offline {
    background-color: #f59e0b;
}

.btn-config {
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 10px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-card);
    color: var(--text-primary);
    font-size: 0.85rem;
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-config:hover {
    background: var(--bg-card-hover);
    border-color: var(--accent-gold);
}

/* Main Content Area */
.main-content {
    flex: 1;
    display: flex;
    flex-direction: column;
    height: 100vh;
    overflow: hidden;
    position: relative;
}

/* Top Header */
.top-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 18px 32px;
    border-bottom: 1px solid var(--border-color);
    background: var(--bg-secondary);
}

.page-title h1 {
    font-size: 1.35rem;
    font-weight: 700;
}

.page-title p {
    font-size: 0.85rem;
    color: var(--text-muted);
    margin-top: 2px;
}

.header-actions {
    display: flex;
    gap: 10px;
}

.action-btn {
    width: 40px;
    height: 40px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-card);
    color: var(--text-secondary);
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s;
}

.action-btn:hover {
    color: var(--text-primary);
    background: var(--bg-card-hover);
    border-color: var(--accent-primary);
}

/* Tab Contents */
.tab-content {
    display: none;
    flex: 1;
    overflow-y: auto;
    padding: 24px 32px;
}

.tab-content.active {
    display: flex;
    flex-direction: column;
}

/* Chat Layout */
.chat-container {
    display: flex;
    flex-direction: column;
    height: 100%;
    max-width: 960px;
    margin: 0 auto;
    width: 100%;
}

.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: 16px 0;
    display: flex;
    flex-direction: column;
    gap: 20px;
}

.message {
    display: flex;
    gap: 14px;
    max-width: 85%;
    animation: fadeIn 0.3s ease;
}

.ai-message {
    align-self: flex-start;
}

.user-message {
    align-self: flex-end;
    flex-direction: row-reverse;
}

.avatar {
    width: 38px;
    height: 38px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.2rem;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    flex-shrink: 0;
}

.bubble {
    padding: 16px 20px;
    border-radius: var(--radius-lg);
    background: var(--bubble-ai);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-sm);
    line-height: 1.6;
    font-size: 0.95rem;
    position: relative;
}

.user-message .bubble {
    background: var(--bubble-user);
    color: #ffffff;
    border: none;
}

.message-content h3 {
    margin-bottom: 8px;
    font-size: 1.1rem;
}

.message-content p {
    margin-bottom: 8px;
}

.message-content ul, .message-content ol {
    padding-left: 20px;
    margin-bottom: 10px;
}

.message-content blockquote {
    border-left: 3px solid var(--accent-gold);
    padding-left: 12px;
    margin: 10px 0;
    color: var(--text-secondary);
    font-style: italic;
}

.quick-prompts {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    margin-top: 14px;
}

.quick-chip {
    padding: 6px 14px;
    background: rgba(255, 255, 255, 0.06);
    border: 1px solid var(--border-color);
    border-radius: 20px;
    color: var(--text-secondary);
    font-size: 0.82rem;
    cursor: pointer;
    transition: all 0.2s;
}

.quick-chip:hover {
    background: var(--accent-red);
    color: #ffffff;
    border-color: var(--accent-red);
}

.chat-input-wrapper {
    padding: 16px 0;
}

.chat-form {
    display: flex;
    gap: 10px;
    background: var(--bg-secondary);
    padding: 8px 12px;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    box-shadow: var(--shadow-md);
}

.chat-form input {
    flex: 1;
    background: transparent;
    border: none;
    outline: none;
    color: var(--text-primary);
    font-size: 0.95rem;
    padding: 8px;
    font-family: inherit;
}

.btn-icon {
    width: 42px;
    height: 42px;
    border-radius: 50%;
    border: none;
    background: rgba(255, 255, 255, 0.05);
    color: var(--text-secondary);
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    transition: all 0.2s;
}

.btn-icon:hover {
    color: var(--accent-red);
    background: rgba(239, 68, 68, 0.15);
}

.btn-icon.recording {
    background: var(--accent-red);
    color: #ffffff;
    animation: pulse 1.5s infinite;
}

.btn-send {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 8px 20px;
    border-radius: var(--radius-md);
    border: none;
    background: var(--accent-gradient);
    color: #ffffff;
    font-weight: 700;
    cursor: pointer;
    transition: all 0.2s;
}

.btn-send:hover {
    opacity: 0.9;
    transform: translateY(-1px);
}

.btn-primary {
    background: var(--accent-gradient);
    color: #ffffff;
    border: none;
    padding: 10px 20px;
    border-radius: var(--radius-md);
    font-weight: 700;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    gap: 8px;
    transition: all 0.2s;
}

.btn-primary:hover {
    opacity: 0.9;
    box-shadow: var(--shadow-glow);
}

.btn-secondary {
    background: var(--bg-card);
    color: var(--text-secondary);
    border: 1px solid var(--border-color);
    padding: 10px 18px;
    border-radius: var(--radius-md);
    font-weight: 600;
    cursor: pointer;
    transition: all 0.2s;
}

/* Speak Button in Bubbles */
.speak-btn {
    background: transparent;
    border: none;
    color: var(--accent-gold);
    cursor: pointer;
    margin-left: 6px;
    font-size: 0.9rem;
    transition: transform 0.2s;
}

.speak-btn:hover {
    transform: scale(1.2);
}

/* Roleplay Tab */
.roleplay-container {
    display: grid;
    grid-template-columns: 320px 1fr;
    gap: 24px;
    height: 100%;
}

.scenario-selector h3 {
    font-size: 1.05rem;
    margin-bottom: 14px;
}

.scenario-grid {
    display: flex;
    flex-direction: column;
    gap: 12px;
}

.scenario-card {
    padding: 16px;
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    cursor: pointer;
    transition: all 0.2s;
}

.scenario-card:hover {
    border-color: var(--accent-gold);
    background: var(--bg-card-hover);
}

.scenario-card.active {
    border-color: var(--accent-red);
    background: rgba(239, 68, 68, 0.1);
    box-shadow: var(--shadow-glow);
}

.scenario-card h4 {
    font-size: 0.95rem;
    margin-bottom: 6px;
}

.scenario-card p {
    font-size: 0.8rem;
    color: var(--text-secondary);
    margin-bottom: 10px;
}

.roles-badge {
    display: flex;
    flex-direction: column;
    gap: 4px;
    font-size: 0.75rem;
    color: var(--text-muted);
}

.roleplay-chat-box {
    display: flex;
    flex-direction: column;
    height: 100%;
    background: var(--bg-secondary);
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
    padding: 20px;
}

.roleplay-messages {
    flex: 1;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: 16px;
    padding-bottom: 16px;
}

/* Vocab & Flashcards */
.vocab-container {
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.search-bar {
    display: flex;
    gap: 10px;
    max-width: 700px;
    margin: 0 auto;
    width: 100%;
}

.search-bar input {
    flex: 1;
    padding: 12px 18px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-primary);
    font-size: 1rem;
}

.sample-cards-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
    gap: 20px;
}

.vocab-card {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 20px;
    display: flex;
    flex-direction: column;
    gap: 10px;
    box-shadow: var(--shadow-sm);
    transition: all 0.2s;
}

.vocab-card:hover {
    transform: translateY(-4px);
    box-shadow: var(--shadow-md);
    border-color: var(--accent-gold);
}

.card-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.hsk-tag {
    font-size: 0.75rem;
    font-weight: 700;
    padding: 4px 8px;
    border-radius: var(--radius-sm);
    background: var(--accent-red);
    color: #ffffff;
}

.audio-btn {
    background: rgba(255, 255, 255, 0.08);
    border: none;
    color: var(--accent-gold);
    width: 32px;
    height: 32px;
    border-radius: 50%;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
}

.card-hanzi {
    font-size: 2.2rem;
    font-weight: 700;
    color: var(--text-primary);
    font-family: 'Noto Sans SC', sans-serif;
}

.card-pinyin {
    font-size: 1.1rem;
    color: var(--accent-gold);
    font-weight: 600;
}

.card-hanviet {
    font-size: 0.95rem;
    color: #38bdf8;
}

.card-vi {
    font-size: 0.95rem;
    color: var(--text-primary);
}

.card-breakdown {
    font-size: 0.85rem;
    color: var(--text-secondary);
    background: rgba(0, 0, 0, 0.2);
    padding: 8px;
    border-radius: var(--radius-sm);
}

.card-example {
    font-size: 0.85rem;
    color: var(--text-secondary);
    border-top: 1px dashed var(--border-color);
    padding-top: 8px;
}

/* Grammar Tab */
.grammar-container {
    max-width: 900px;
    margin: 0 auto;
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.grammar-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 14px;
}

.grammar-card h3 {
    font-size: 1.15rem;
}

.subtitle {
    font-size: 0.85rem;
    color: var(--text-muted);
}

.grammar-card textarea {
    width: 100%;
    padding: 16px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 1rem;
    font-family: inherit;
    resize: vertical;
}

.grammar-result {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    line-height: 1.7;
    display: none;
}

/* HSK Quiz Tab */
.hsk-container {
    max-width: 900px;
    margin: 0 auto;
    width: 100%;
    display: flex;
    flex-direction: column;
    gap: 24px;
}

.hsk-controls {
    display: flex;
    gap: 16px;
    align-items: flex-end;
    background: var(--bg-secondary);
    padding: 20px;
    border-radius: var(--radius-lg);
    border: 1px solid var(--border-color);
}

.control-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
    flex: 1;
}

.control-group label {
    font-size: 0.85rem;
    font-weight: 600;
    color: var(--text-secondary);
}

.control-group select, .control-group input {
    padding: 10px 14px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
    font-size: 0.9rem;
}

.quiz-box {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 24px;
    min-height: 300px;
}

.placeholder-box {
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    text-align: center;
    height: 250px;
    color: var(--text-muted);
}

.big-icon {
    font-size: 3.5rem;
    margin-bottom: 16px;
    color: var(--accent-gold);
}

.question-item {
    background: var(--bg-card);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-md);
    padding: 20px;
    margin-bottom: 20px;
}

.q-header {
    font-size: 1.15rem;
    font-weight: 700;
    margin-bottom: 6px;
    display: flex;
    align-items: center;
    gap: 10px;
}

.q-pinyin {
    color: var(--accent-gold);
    font-size: 0.95rem;
    margin-bottom: 4px;
}

.q-vi {
    color: var(--text-secondary);
    font-size: 0.9rem;
    margin-bottom: 14px;
}

.options-list {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: 10px;
}

.option-btn {
    padding: 12px 16px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-secondary);
    color: var(--text-primary);
    text-align: left;
    cursor: pointer;
    transition: all 0.2s;
    display: flex;
    align-items: center;
    gap: 10px;
}

.option-btn:hover {
    background: var(--bg-card-hover);
    border-color: var(--accent-primary);
}

.option-btn.correct {
    background: #065f46 !important;
    border-color: #10b981 !important;
    color: #ffffff;
}

.option-btn.wrong {
    background: #881337 !important;
    border-color: #f43f5e !important;
    color: #ffffff;
}

.q-explanation {
    margin-top: 14px;
    padding: 12px;
    border-radius: var(--radius-sm);
    background: rgba(0, 0, 0, 0.2);
    border-left: 3px solid #10b981;
    font-size: 0.9rem;
    display: none;
}

/* Han-Viet Rules */
.rules-container {
    max-width: 960px;
    margin: 0 auto;
    width: 100%;
}

.rules-intro {
    text-align: center;
    margin-bottom: 30px;
}

.rules-intro h2 {
    font-size: 1.5rem;
    margin-bottom: 8px;
    background: var(--accent-gradient);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
}

.rules-intro p {
    color: var(--text-secondary);
}

.rules-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(400px, 1fr));
    gap: 20px;
}

.rule-card {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    padding: 20px;
    position: relative;
    box-shadow: var(--shadow-sm);
}

.rule-icon {
    font-size: 1.4rem;
    color: var(--accent-gold);
    margin-bottom: 10px;
}

.rule-card h4 {
    font-size: 1rem;
    margin-bottom: 10px;
    color: #38bdf8;
}

.rule-example {
    font-size: 0.9rem;
    color: var(--text-secondary);
    background: rgba(0, 0, 0, 0.15);
    padding: 10px;
    border-radius: var(--radius-sm);
    line-height: 1.6;
}

/* Modal */
.modal {
    position: fixed;
    top: 0;
    left: 0;
    width: 100vw;
    height: 100vh;
    background: rgba(0, 0, 0, 0.65);
    backdrop-filter: blur(6px);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 1000;
}

.modal.active {
    display: flex;
}

.modal-content {
    background: var(--bg-secondary);
    border: 1px solid var(--border-color);
    border-radius: var(--radius-lg);
    width: 90%;
    max-width: 480px;
    box-shadow: var(--shadow-md);
    overflow: hidden;
}

.modal-header {
    display: flex;
    justify-content: space-between;
    align-items: center;
    padding: 16px 24px;
    border-bottom: 1px solid var(--border-color);
}

.close-modal {
    background: transparent;
    border: none;
    color: var(--text-muted);
    font-size: 1.5rem;
    cursor: pointer;
}

.modal-body {
    padding: 24px;
    display: flex;
    flex-direction: column;
    gap: 16px;
}

.form-group {
    display: flex;
    flex-direction: column;
    gap: 6px;
}

.form-group label {
    font-size: 0.85rem;
    font-weight: 600;
}

.form-group input, .form-group select {
    padding: 10px 14px;
    border-radius: var(--radius-md);
    border: 1px solid var(--border-color);
    background: var(--bg-primary);
    color: var(--text-primary);
}

.form-group small {
    font-size: 0.75rem;
    color: var(--text-muted);
}

.modal-alert {
    font-size: 0.85rem;
    padding: 8px 12px;
    border-radius: var(--radius-sm);
    display: none;
}

.modal-footer {
    display: flex;
    justify-content: flex-end;
    gap: 10px;
    padding: 16px 24px;
    border-top: 1px solid var(--border-color);
    background: rgba(0, 0, 0, 0.1);
}

/* Animations */
@keyframes fadeIn {
    from { opacity: 0; transform: translateY(8px); }
    to { opacity: 1; transform: translateY(0); }
}

@keyframes pulse {
    0% { transform: scale(1); }
    50% { transform: scale(1.1); }
    100% { transform: scale(1); }
}

/* Responsive */
@media (max-width: 900px) {
    .app-container {
        flex-direction: column;
    }
    .sidebar {
        width: 100%;
        height: auto;
        padding: 12px;
    }
    .roleplay-container {
        grid-template-columns: 1fr;
    }
    .options-list {
        grid-template-columns: 1fr;
    }
}