/* ============================================================
   智能传感与信号处理 — 智能教学平台 设计系统
   暗色科技风 + Glassmorphism
   ============================================================ */

/* ---- CSS变量 / 设计令牌 ---- */
:root {
    /* 色彩 */
    --bg-primary: #0a0a1a;
    --bg-secondary: #111128;
    --bg-tertiary: #1a1a2e;
    --bg-card: rgba(22, 22, 50, 0.6);
    --bg-glass: rgba(255, 255, 255, 0.04);
    --bg-glass-hover: rgba(255, 255, 255, 0.08);
    --border-glass: rgba(255, 255, 255, 0.08);
    --border-glass-hover: rgba(255, 255, 255, 0.15);

    --accent-blue: #00d4ff;
    --accent-purple: #7c3aed;
    --accent-cyan: #06b6d4;
    --accent-pink: #ec4899;
    --accent-green: #10b981;
    --accent-yellow: #f59e0b;
    --accent-red: #ef4444;
    --accent-orange: #f97316;

    --gradient-primary: linear-gradient(135deg, #00d4ff 0%, #7c3aed 100%);
    --gradient-bg: linear-gradient(135deg, #0a0a1a 0%, #1a1a2e 50%, #0f0f23 100%);
    --gradient-card: linear-gradient(135deg, rgba(0,212,255,0.05) 0%, rgba(124,58,237,0.05) 100%);

    --text-primary: #f0f0f8;
    --text-secondary: #a0a0c0;
    --text-tertiary: #6b6b8a;
    --text-accent: #00d4ff;

    /* 间距 */
    --space-xs: 4px;
    --space-sm: 8px;
    --space-md: 16px;
    --space-lg: 24px;
    --space-xl: 32px;
    --space-2xl: 48px;

    /* 圆角 */
    --radius-sm: 8px;
    --radius-md: 12px;
    --radius-lg: 16px;
    --radius-xl: 20px;
    --radius-full: 9999px;

    /* 阴影 */
    --shadow-sm: 0 2px 8px rgba(0,0,0,0.3);
    --shadow-md: 0 4px 16px rgba(0,0,0,0.4);
    --shadow-lg: 0 8px 32px rgba(0,0,0,0.5);
    --shadow-glow-blue: 0 0 20px rgba(0,212,255,0.3);
    --shadow-glow-purple: 0 0 20px rgba(124,58,237,0.3);

    /* 字体 */
    --font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;

    /* 动画 */
    --transition-fast: 0.15s ease;
    --transition-normal: 0.3s ease;
    --transition-slow: 0.5s ease;

    /* 布局 */
    --navbar-height: 64px;
}

/* ---- 基础重置 ---- */
*, *::before, *::after {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

html {
    font-size: 16px;
    scroll-behavior: smooth;
}

body {
    font-family: var(--font-family);
    background: var(--gradient-bg);
    color: var(--text-primary);
    min-height: 100vh;
    overflow-x: hidden;
    line-height: 1.6;
    -webkit-font-smoothing: antialiased;
}

/* ---- 背景粒子画布 ---- */
#bg-canvas {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    z-index: 0;
    pointer-events: none;
}

/* ---- 滚动条 ---- */
::-webkit-scrollbar {
    width: 6px;
    height: 6px;
}
::-webkit-scrollbar-track {
    background: transparent;
}
::-webkit-scrollbar-thumb {
    background: rgba(255,255,255,0.1);
    border-radius: 3px;
}
::-webkit-scrollbar-thumb:hover {
    background: rgba(255,255,255,0.2);
}

/* ============================================================
   导航栏
   ============================================================ */
.navbar {
    position: fixed;
    top: 0;
    left: 0;
    right: 0;
    height: var(--navbar-height);
    z-index: 100;
    background: rgba(10, 10, 26, 0.85);
    backdrop-filter: blur(20px) saturate(1.5);
    -webkit-backdrop-filter: blur(20px) saturate(1.5);
    border-bottom: 1px solid var(--border-glass);
}

.navbar-inner {
    max-width: 1440px;
    margin: 0 auto;
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: space-between;
    padding: 0 var(--space-lg);
}

.navbar-brand {
    display: flex;
    align-items: center;
    gap: var(--space-md);
}

.logo-icon {
    width: 40px;
    height: 40px;
    flex-shrink: 0;
    animation: logoPulse 3s ease-in-out infinite;
}

@keyframes logoPulse {
    0%, 100% { filter: drop-shadow(0 0 4px rgba(0,212,255,0.4)); }
    50% { filter: drop-shadow(0 0 12px rgba(0,212,255,0.8)); }
}

.brand-text {
    display: flex;
    flex-direction: column;
    line-height: 1.2;
}

.brand-title {
    font-size: 1.05rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.brand-subtitle {
    font-size: 0.72rem;
    color: var(--text-tertiary);
    letter-spacing: 2px;
    text-transform: uppercase;
}

.navbar-nav {
    display: flex;
    gap: var(--space-sm);
}

.nav-btn {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: 10px 22px;
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-full);
    background: var(--bg-glass);
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: 0.9rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.nav-btn::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--gradient-primary);
    opacity: 0;
    transition: opacity var(--transition-normal);
    border-radius: inherit;
}

.nav-btn:hover {
    border-color: var(--border-glass-hover);
    color: var(--text-primary);
    transform: translateY(-1px);
}

.nav-btn.active {
    border-color: rgba(0,212,255,0.3);
    color: #fff;
    background: linear-gradient(135deg, rgba(0,212,255,0.15), rgba(124,58,237,0.15));
    box-shadow: var(--shadow-glow-blue);
}

.nav-btn.active::before {
    opacity: 0.1;
}

.nav-icon {
    font-size: 1.1rem;
    position: relative;
    z-index: 1;
}

.nav-label {
    position: relative;
    z-index: 1;
}

.navbar-extra {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
}

.status-dot {
    width: 8px;
    height: 8px;
    background: var(--accent-green);
    border-radius: 50%;
}

.status-dot.pulse {
    animation: statusPulse 2s ease-in-out infinite;
}

@keyframes statusPulse {
    0%, 100% { box-shadow: 0 0 0 0 rgba(16,185,129,0.4); }
    50% { box-shadow: 0 0 0 6px rgba(16,185,129,0); }
}

.status-text {
    font-size: 0.78rem;
    color: var(--text-tertiary);
}

/* ============================================================
   主内容区
   ============================================================ */
.main-content {
    position: relative;
    z-index: 1;
    margin-top: var(--navbar-height);
    min-height: calc(100vh - var(--navbar-height));
}

.module {
    display: none;
    animation: fadeInModule 0.4s ease;
}

.module.active {
    display: block;
}

@keyframes fadeInModule {
    from { opacity: 0; transform: translateY(12px); }
    to { opacity: 1; transform: translateY(0); }
}

/* ============================================================
   Glassmorphism 卡片
   ============================================================ */
.glass-card {
    background: var(--bg-card);
    backdrop-filter: blur(16px) saturate(1.2);
    -webkit-backdrop-filter: blur(16px) saturate(1.2);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    transition: all var(--transition-normal);
}

.glass-card:hover {
    border-color: var(--border-glass-hover);
    background: var(--bg-glass-hover);
    box-shadow: var(--shadow-md);
}

/* ============================================================
   问答模块
   ============================================================ */
.chat-container {
    display: flex;
    height: calc(100vh - var(--navbar-height));
    max-width: 1440px;
    margin: 0 auto;
}

.chat-main {
    flex: 1;
    display: flex;
    flex-direction: column;
    min-width: 0;
}

/* --- 难度切换栏 --- */
.difficulty-bar {
    display: flex;
    align-items: center;
    padding: var(--space-md) var(--space-lg);
    border-bottom: 1px solid var(--border-glass);
    background: rgba(10,10,26,0.5);
    backdrop-filter: blur(10px);
    gap: var(--space-md);
}

.difficulty-label {
    font-size: 0.85rem;
    color: var(--text-secondary);
    white-space: nowrap;
}

.difficulty-switch {
    display: flex;
    gap: var(--space-xs);
    background: var(--bg-glass);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-full);
    padding: 3px;
}

.diff-btn {
    display: flex;
    align-items: center;
    gap: 6px;
    padding: 6px 16px;
    border: none;
    border-radius: var(--radius-full);
    background: transparent;
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: 0.82rem;
    font-weight: 500;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.diff-btn:hover {
    color: var(--text-primary);
    background: rgba(255,255,255,0.05);
}

.diff-btn.active {
    background: rgba(255,255,255,0.1);
    color: #fff;
    box-shadow: var(--shadow-sm);
}

.diff-btn.active[data-level="beginner"] {
    background: rgba(16,185,129,0.2);
    color: #34d399;
}
.diff-btn.active[data-level="intermediate"] {
    background: rgba(245,158,11,0.2);
    color: #fbbf24;
}
.diff-btn.active[data-level="advanced"] {
    background: rgba(239,68,68,0.2);
    color: #f87171;
}

.diff-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
}

.diff-dot.green { background: var(--accent-green); }
.diff-dot.yellow { background: var(--accent-yellow); }
.diff-dot.red { background: var(--accent-red); }

.clear-btn {
    margin-left: auto;
    padding: 6px 14px;
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-full);
    background: transparent;
    color: var(--text-tertiary);
    font-family: var(--font-family);
    font-size: 0.78rem;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.clear-btn:hover {
    border-color: rgba(239,68,68,0.3);
    color: var(--accent-red);
    background: rgba(239,68,68,0.1);
}

/* --- 消息列表 --- */
.chat-messages {
    flex: 1;
    overflow-y: auto;
    padding: var(--space-lg);
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
}

/* 欢迎消息 */
.welcome-message {
    text-align: center;
    padding: var(--space-2xl) var(--space-lg);
    animation: fadeInUp 0.6s ease;
}

@keyframes fadeInUp {
    from { opacity: 0; transform: translateY(20px); }
    to { opacity: 1; transform: translateY(0); }
}

.welcome-icon {
    font-size: 3rem;
    margin-bottom: var(--space-md);
    animation: float 3s ease-in-out infinite;
}

@keyframes float {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-8px); }
}

.welcome-message h2 {
    font-size: 1.4rem;
    font-weight: 700;
    margin-bottom: var(--space-sm);
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.welcome-message p {
    color: var(--text-secondary);
    font-size: 0.92rem;
    max-width: 480px;
    margin: 0 auto var(--space-lg);
}

.quick-questions {
    display: flex;
    flex-wrap: wrap;
    justify-content: center;
    gap: var(--space-sm);
}

.quick-q {
    padding: 8px 18px;
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-full);
    background: var(--bg-glass);
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: 0.82rem;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.quick-q:hover {
    border-color: var(--accent-blue);
    color: var(--accent-blue);
    background: rgba(0,212,255,0.08);
    transform: translateY(-2px);
    box-shadow: 0 4px 12px rgba(0,212,255,0.15);
}

/* --- 消息气泡 --- */
.message {
    display: flex;
    gap: var(--space-md);
    max-width: 85%;
    animation: msgIn 0.35s ease;
}

@keyframes msgIn {
    from { opacity: 0; transform: translateY(10px); }
    to { opacity: 1; transform: translateY(0); }
}

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

.message-avatar {
    width: 36px;
    height: 36px;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 1.1rem;
    flex-shrink: 0;
}

.message.user .message-avatar {
    background: linear-gradient(135deg, var(--accent-blue), var(--accent-purple));
}

.message.assistant .message-avatar {
    background: linear-gradient(135deg, var(--accent-purple), var(--accent-pink));
}

.message-bubble {
    padding: var(--space-md) var(--space-lg);
    border-radius: var(--radius-lg);
    font-size: 0.92rem;
    line-height: 1.7;
    position: relative;
}

.message.user .message-bubble {
    background: linear-gradient(135deg, rgba(0,212,255,0.15), rgba(124,58,237,0.15));
    border: 1px solid rgba(0,212,255,0.2);
    border-top-right-radius: var(--space-xs);
}

.message.assistant .message-bubble {
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-top-left-radius: var(--space-xs);
}

/* Markdown 内容样式 */
.message-bubble h1, .message-bubble h2, .message-bubble h3 {
    margin: var(--space-md) 0 var(--space-sm);
    color: var(--text-primary);
}
.message-bubble h1 { font-size: 1.3rem; }
.message-bubble h2 { font-size: 1.15rem; }
.message-bubble h3 { font-size: 1.05rem; }

.message-bubble p {
    margin-bottom: var(--space-sm);
}

.message-bubble code {
    background: rgba(0,212,255,0.1);
    padding: 2px 6px;
    border-radius: 4px;
    font-size: 0.85em;
    color: var(--accent-blue);
}

.message-bubble pre {
    background: rgba(0,0,0,0.3);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-sm);
    padding: var(--space-md);
    overflow-x: auto;
    margin: var(--space-sm) 0;
}

.message-bubble pre code {
    background: none;
    padding: 0;
    color: var(--text-primary);
}

.message-bubble ul, .message-bubble ol {
    padding-left: var(--space-lg);
    margin-bottom: var(--space-sm);
}

.message-bubble li {
    margin-bottom: var(--space-xs);
}

.message-bubble blockquote {
    border-left: 3px solid var(--accent-blue);
    padding-left: var(--space-md);
    margin: var(--space-sm) 0;
    color: var(--text-secondary);
}

.message-bubble strong {
    color: var(--accent-blue);
    font-weight: 600;
}

.message-bubble table {
    width: 100%;
    border-collapse: collapse;
    margin: var(--space-sm) 0;
}
.message-bubble th, .message-bubble td {
    border: 1px solid var(--border-glass);
    padding: 8px 12px;
    text-align: left;
}
.message-bubble th {
    background: rgba(0,212,255,0.08);
    font-weight: 600;
}

/* 打字光标 */
.typing-cursor {
    display: inline-block;
    width: 2px;
    height: 1em;
    background: var(--accent-blue);
    margin-left: 2px;
    animation: blink 0.8s ease-in-out infinite;
    vertical-align: text-bottom;
}

@keyframes blink {
    0%, 100% { opacity: 1; }
    50% { opacity: 0; }
}

/* 加载动画 */
.loading-dots {
    display: flex;
    gap: 6px;
    padding: var(--space-md);
}
.loading-dots span {
    width: 8px;
    height: 8px;
    background: var(--accent-blue);
    border-radius: 50%;
    animation: dotBounce 1.4s ease-in-out infinite;
}
.loading-dots span:nth-child(2) { animation-delay: 0.2s; }
.loading-dots span:nth-child(3) { animation-delay: 0.4s; }

@keyframes dotBounce {
    0%, 80%, 100% { transform: scale(0.6); opacity: 0.4; }
    40% { transform: scale(1); opacity: 1; }
}

/* --- 输入区域 --- */
.chat-input-area {
    padding: var(--space-md) var(--space-lg) var(--space-lg);
    border-top: 1px solid var(--border-glass);
    background: rgba(10,10,26,0.5);
    backdrop-filter: blur(10px);
}

.input-wrapper {
    display: flex;
    align-items: flex-end;
    gap: var(--space-sm);
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: var(--space-sm);
    transition: border-color var(--transition-normal);
}

.input-wrapper:focus-within {
    border-color: var(--accent-blue);
    box-shadow: 0 0 0 3px rgba(0,212,255,0.1);
}

#chat-input {
    flex: 1;
    background: none;
    border: none;
    outline: none;
    color: var(--text-primary);
    font-family: var(--font-family);
    font-size: 0.92rem;
    resize: none;
    max-height: 120px;
    padding: var(--space-sm) var(--space-md);
    line-height: 1.5;
}

#chat-input::placeholder {
    color: var(--text-tertiary);
}

.send-btn {
    width: 40px;
    height: 40px;
    border: none;
    border-radius: var(--radius-md);
    background: var(--gradient-primary);
    color: #fff;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    flex-shrink: 0;
    transition: all var(--transition-normal);
}

.send-btn:hover {
    transform: scale(1.05);
    box-shadow: var(--shadow-glow-blue);
}

.send-btn:active {
    transform: scale(0.95);
}

.send-btn:disabled {
    opacity: 0.5;
    cursor: not-allowed;
    transform: none;
}

.send-btn svg {
    width: 18px;
    height: 18px;
}

.input-hint {
    font-size: 0.72rem;
    color: var(--text-tertiary);
    text-align: right;
    margin-top: var(--space-xs);
}

/* --- 右侧知识面板 --- */
.chat-sidebar {
    width: 320px;
    border-left: 1px solid var(--border-glass);
    padding: var(--space-lg);
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    gap: var(--space-lg);
    background: rgba(10,10,26,0.3);
}

.sidebar-section {
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
}

.sidebar-title {
    font-size: 0.92rem;
    font-weight: 600;
    margin-bottom: var(--space-md);
    color: var(--text-primary);
}

.knowledge-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.knowledge-item {
    padding: var(--space-sm) var(--space-md);
    background: var(--bg-glass);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-sm);
    font-size: 0.82rem;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-normal);
}

.knowledge-item:hover {
    border-color: var(--accent-blue);
    color: var(--accent-blue);
    background: rgba(0,212,255,0.05);
}

.experiment-links {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.exp-link-card {
    display: flex;
    align-items: center;
    gap: var(--space-sm);
    padding: var(--space-sm) var(--space-md);
    background: var(--bg-glass);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-sm);
    font-size: 0.82rem;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-normal);
}

.exp-link-card:hover {
    border-color: var(--accent-purple);
    color: var(--accent-purple);
    background: rgba(124,58,237,0.05);
    transform: translateX(4px);
}

.exp-link-icon {
    font-size: 1.2rem;
}

.empty-hint {
    font-size: 0.82rem;
    color: var(--text-tertiary);
    text-align: center;
    padding: var(--space-lg);
}

/* ============================================================
   仿真实验模块
   ============================================================ */

/* --- 实验选择网格 --- */
.experiment-grid-container {
    max-width: 1200px;
    margin: 0 auto;
    padding: var(--space-2xl) var(--space-lg);
}

.section-header {
    text-align: center;
    margin-bottom: var(--space-2xl);
}

.section-title {
    font-size: 1.8rem;
    font-weight: 800;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    margin-bottom: var(--space-sm);
}

.section-desc {
    color: var(--text-secondary);
    font-size: 0.95rem;
}

.experiment-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(220px, 1fr));
    gap: var(--space-lg);
}

.exp-card {
    background: var(--bg-card);
    backdrop-filter: blur(16px);
    -webkit-backdrop-filter: blur(16px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-xl);
    padding: var(--space-xl) var(--space-lg);
    text-align: center;
    cursor: pointer;
    transition: all var(--transition-normal);
    position: relative;
    overflow: hidden;
}

.exp-card::before {
    content: '';
    position: absolute;
    top: 0;
    left: 0;
    right: 0;
    height: 3px;
    background: var(--gradient-primary);
    opacity: 0;
    transition: opacity var(--transition-normal);
}

.exp-card:hover {
    border-color: rgba(0,212,255,0.3);
    transform: translateY(-6px);
    box-shadow: 0 12px 40px rgba(0,212,255,0.1);
}

.exp-card:hover::before {
    opacity: 1;
}

.exp-card-icon {
    font-size: 2.8rem;
    margin-bottom: var(--space-md);
    display: block;
    filter: drop-shadow(0 0 8px rgba(0,212,255,0.3));
    transition: transform var(--transition-normal);
}

.exp-card:hover .exp-card-icon {
    transform: scale(1.15);
}

.exp-card-name {
    font-size: 0.95rem;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: var(--space-xs);
}

.exp-card-desc {
    font-size: 0.78rem;
    color: var(--text-tertiary);
}

/* --- 实验工作区 --- */
.experiment-workspace {
    max-width: 1440px;
    margin: 0 auto;
    padding: var(--space-md) var(--space-lg);
}

.experiment-workspace.hidden {
    display: none;
}

.exp-topbar {
    display: flex;
    align-items: center;
    gap: var(--space-lg);
    margin-bottom: var(--space-lg);
    padding-bottom: var(--space-md);
    border-bottom: 1px solid var(--border-glass);
}

.back-btn {
    padding: 8px 18px;
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-full);
    background: var(--bg-glass);
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: 0.85rem;
    cursor: pointer;
    transition: all var(--transition-normal);
    white-space: nowrap;
}

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

.exp-title {
    flex: 1;
    font-size: 1.3rem;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

.exp-actions {
    display: flex;
    gap: var(--space-sm);
}

.action-btn {
    padding: 8px 16px;
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-full);
    background: var(--bg-glass);
    color: var(--text-secondary);
    font-family: var(--font-family);
    font-size: 0.82rem;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.action-btn:hover {
    border-color: var(--accent-blue);
    color: var(--accent-blue);
    background: rgba(0,212,255,0.08);
}

/* 实验内容布局 */
.exp-body {
    display: flex;
    gap: var(--space-lg);
    margin-bottom: var(--space-lg);
}

.exp-canvas-wrap {
    flex: 1;
    min-width: 0;
    position: relative;
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
}

#exp-canvas {
    display: block;
    width: 100%;
    height: auto;
    max-height: 420px;
}

.canvas-overlay {
    position: absolute;
    bottom: var(--space-sm);
    right: var(--space-sm);
    font-size: 0.72rem;
    color: var(--text-tertiary);
    pointer-events: none;
}

/* 参数控制面板 */
.exp-controls {
    width: 320px;
    flex-shrink: 0;
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
    overflow-y: auto;
    max-height: 460px;
}

.panel-title {
    font-size: 1rem;
    font-weight: 600;
    margin-bottom: var(--space-lg);
    color: var(--text-primary);
}

/* 参数项 */
.param-group {
    margin-bottom: var(--space-lg);
}

.param-label {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-bottom: var(--space-sm);
    font-size: 0.82rem;
    color: var(--text-secondary);
}

.param-value {
    color: var(--accent-blue);
    font-weight: 600;
    font-variant-numeric: tabular-nums;
}

/* 自定义滑块 */
.param-slider {
    -webkit-appearance: none;
    appearance: none;
    width: 100%;
    height: 6px;
    background: rgba(255,255,255,0.06);
    border-radius: 3px;
    outline: none;
    cursor: pointer;
    position: relative;
}

.param-slider::-webkit-slider-thumb {
    -webkit-appearance: none;
    appearance: none;
    width: 18px;
    height: 18px;
    background: var(--gradient-primary);
    border-radius: 50%;
    cursor: grab;
    box-shadow: 0 0 10px rgba(0,212,255,0.4);
    transition: box-shadow var(--transition-fast);
}

.param-slider::-webkit-slider-thumb:hover {
    box-shadow: 0 0 16px rgba(0,212,255,0.6);
    transform: scale(1.1);
}

.param-slider::-moz-range-thumb {
    width: 18px;
    height: 18px;
    background: var(--gradient-primary);
    border-radius: 50%;
    border: none;
    cursor: grab;
    box-shadow: 0 0 10px rgba(0,212,255,0.4);
}

/* 下拉选择 */
.param-select {
    width: 100%;
    padding: 8px 12px;
    background: var(--bg-glass);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-sm);
    color: var(--text-primary);
    font-family: var(--font-family);
    font-size: 0.85rem;
    outline: none;
    cursor: pointer;
    transition: border-color var(--transition-normal);
}

.param-select:focus {
    border-color: var(--accent-blue);
}

.param-select option {
    background: var(--bg-secondary);
    color: var(--text-primary);
}

/* 公式框 */
.formula-box {
    margin-top: var(--space-lg);
    padding: var(--space-md);
    background: rgba(0,212,255,0.04);
    border: 1px solid rgba(0,212,255,0.1);
    border-radius: var(--radius-md);
}

.formula-box h4 {
    font-size: 0.85rem;
    font-weight: 600;
    margin-bottom: var(--space-sm);
    color: var(--accent-blue);
}

.formula-text {
    font-family: 'Courier New', monospace;
    font-size: 0.85rem;
    color: var(--text-secondary);
    line-height: 1.8;
    word-break: break-all;
}

.formula-text .highlight {
    color: var(--accent-blue);
    font-weight: 600;
}

/* 图表区域 */
.exp-charts {
    display: grid;
    grid-template-columns: 1fr 1fr;
    gap: var(--space-lg);
}

.chart-card {
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: var(--space-lg);
}

.chart-title {
    font-size: 0.88rem;
    font-weight: 600;
    margin-bottom: var(--space-md);
    color: var(--text-secondary);
}

.chart-card canvas {
    width: 100% !important;
    max-height: 260px;
}

/* ============================================================
   通用按钮
   ============================================================ */
.btn-primary {
    padding: 10px 24px;
    border: none;
    border-radius: var(--radius-full);
    background: var(--gradient-primary);
    color: #fff;
    font-family: var(--font-family);
    font-size: 0.88rem;
    font-weight: 600;
    cursor: pointer;
    transition: all var(--transition-normal);
}

.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow-blue);
}

/* ============================================================
   响应式
   ============================================================ */
@media (max-width: 1024px) {
    .chat-sidebar {
        display: none;
    }

    .exp-body {
        flex-direction: column;
    }

    .exp-controls {
        width: 100%;
        max-height: none;
    }

    .exp-charts {
        grid-template-columns: 1fr;
    }
}

@media (max-width: 768px) {
    .navbar-inner {
        padding: 0 var(--space-md);
    }

    .brand-text {
        display: none;
    }

    .nav-label {
        display: none;
    }

    .navbar-extra {
        display: none;
    }

    .experiment-grid {
        grid-template-columns: repeat(2, 1fr);
        gap: var(--space-md);
    }

    .exp-topbar {
        flex-wrap: wrap;
    }

    .difficulty-bar {
        flex-wrap: wrap;
    }

    .chat-messages {
        padding: var(--space-md);
    }

    .message {
        max-width: 95%;
    }

    .chat-input-area {
        padding: var(--space-sm) var(--space-md) var(--space-md);
    }
}

@media (max-width: 480px) {
    .experiment-grid {
        grid-template-columns: 1fr;
    }

    .exp-card {
        padding: var(--space-lg) var(--space-md);
    }
}

/* ============================================================
   工具 / 动画辅助
   ============================================================ */
.hidden {
    display: none !important;
}

.fade-in {
    animation: fadeIn 0.4s ease;
}

@keyframes fadeIn {
    from { opacity: 0; }
    to { opacity: 1; }
}

/* 渐变文字 */
.gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* 发光边框 */
.glow-border {
    box-shadow: 0 0 15px rgba(0,212,255,0.15), inset 0 0 15px rgba(0,212,255,0.05);
}

/* 脉冲动画 */
@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.6; }
}

/* Shimmer 加载动画 */
.shimmer {
    background: linear-gradient(90deg, transparent 0%, rgba(255,255,255,0.05) 50%, transparent 100%);
    background-size: 200% 100%;
    animation: shimmer 2s ease-in-out infinite;
}

@keyframes shimmer {
    from { background-position: -200% 0; }
    to { background-position: 200% 0; }
}

/* --- 档位说明卡片 --- */
.level-info-list {
    display: flex;
    flex-direction: column;
    gap: var(--space-sm);
}

.level-info-item {
    padding: 10px 12px;
    background: rgba(255, 255, 255, 0.03);
    border: 1px solid var(--border-glass);
    border-left: 3px solid var(--level-color, #666);
    border-radius: var(--radius-sm);
    transition: all var(--transition-normal);
}

.level-info-item:hover {
    background: rgba(255, 255, 255, 0.06);
    border-color: var(--level-color, #666);
}

.level-info-header {
    display: flex;
    align-items: center;
    gap: 8px;
    margin-bottom: 4px;
}

.level-info-header .level-dot {
    width: 8px;
    height: 8px;
    border-radius: 50%;
    flex-shrink: 0;
}

.level-info-header strong {
    font-size: 0.85rem;
    color: var(--text-primary);
}

.level-info-desc {
    font-size: 0.78rem;
    color: var(--text-tertiary);
    line-height: 1.5;
    margin: 0;
}

/* ============ 消息复制按钮 ============ */
.message.assistant .message-bubble {
    position: relative;
    padding-bottom: 28px; /* 为复制按钮预留空间 */
}

.copy-btn {
    position: absolute;
    right: 12px;
    bottom: 6px;
    background: rgba(255, 255, 255, 0.05);
    border: 1px solid rgba(255, 255, 255, 0.12);
    color: rgba(255, 255, 255, 0.5);
    padding: 3px 8px;
    border-radius: 4px;
    font-size: 10px;
    font-family: 'Inter', system-ui, sans-serif;
    cursor: pointer;
    transition: all 0.2s cubic-bezier(0.4, 0, 0.2, 1);
    display: flex;
    align-items: center;
    gap: 4px;
}

.copy-btn:hover {
    background: rgba(0, 212, 255, 0.15);
    border-color: rgba(0, 212, 255, 0.3);
    color: #00d4ff;
    box-shadow: 0 0 8px rgba(0, 212, 255, 0.2);
}

.copy-btn.copied {
    background: rgba(16, 185, 129, 0.15);
    border-color: rgba(16, 185, 129, 0.3);
    color: #10b981;
    box-shadow: 0 0 8px rgba(16, 185, 129, 0.2);
}

/* ============ 仿真全屏工作区样式 ============ */
#experiment-workspace:fullscreen {
    padding: 24px;
    background: radial-gradient(circle at center, #15152a 0%, #070712 100%) !important;
    overflow-y: auto;
    display: flex;
    flex-direction: column;
    height: 100vh !important;
    width: 100vw !important;
    box-sizing: border-box;
}

#experiment-workspace:fullscreen .exp-topbar {
    margin-bottom: 16px;
}

#experiment-workspace:fullscreen .exp-body {
    flex: 1;
    display: flex;
    gap: 20px;
    min-height: 0; /* 允许子元素在 flex 容器中收缩 */
    margin-bottom: 20px;
}

#experiment-workspace:fullscreen .exp-canvas-wrap {
    flex: 3;
    display: flex;
    align-items: center;
    justify-content: center;
    background: rgba(255, 255, 255, 0.02);
    border-radius: 8px;
    border: 1px solid rgba(255, 255, 255, 0.05);
    padding: 10px;
}

#experiment-workspace:fullscreen #exp-canvas {
    max-width: 100%;
    max-height: 100%;
    object-fit: contain;
}

#experiment-workspace:fullscreen .exp-controls {
    flex: 2;
    overflow-y: auto;
}

#experiment-workspace:fullscreen .exp-charts {
    height: 240px;
    flex-shrink: 0;
}

/* ============================================================
   B站视频弹窗样式
   ============================================================ */
.video-modal-overlay {
    position: fixed;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    background: rgba(10, 10, 26, 0.85);
    backdrop-filter: blur(8px);
    z-index: 2000;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    pointer-events: none;
    transition: opacity var(--transition-normal);
}

.video-modal-overlay.active {
    opacity: 1;
    pointer-events: auto;
}

.video-modal-content {
    background: var(--bg-secondary);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    width: 90%;
    max-width: 800px;
    box-shadow: var(--shadow-lg), var(--shadow-glow-purple);
    display: flex;
    flex-direction: column;
    overflow: hidden;
    transform: scale(0.9);
    transition: transform var(--transition-normal);
}

.video-modal-overlay.active .video-modal-content {
    transform: scale(1);
}

.video-modal-header {
    padding: var(--space-md) var(--space-lg);
    border-bottom: 1px solid var(--border-glass);
    display: flex;
    justify-content: space-between;
    align-items: center;
}

.video-modal-title {
    font-size: 1.1rem;
    font-weight: 600;
    color: var(--text-primary);
}

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

.video-modal-close:hover {
    color: var(--accent-red);
}

.video-modal-body {
    position: relative;
    padding-bottom: 56.25%; /* 16:9 Aspect Ratio */
    height: 0;
    overflow: hidden;
    background: #000;
}

.video-modal-body iframe {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    border: none;
}

.video-modal-footer {
    padding: var(--space-md) var(--space-lg);
    border-top: 1px solid var(--border-glass);
    display: flex;
    justify-content: flex-end;
    background: rgba(0, 0, 0, 0.2);
}

.video-btn {
    background: var(--gradient-primary);
    color: var(--text-primary);
    border: none;
    padding: var(--space-sm) var(--space-lg);
    border-radius: var(--radius-md);
    font-size: 0.9rem;
    font-weight: 500;
    text-decoration: none;
    cursor: pointer;
    box-shadow: var(--shadow-sm);
    transition: all var(--transition-fast);
    display: inline-flex;
    align-items: center;
    gap: 8px;
}

.video-btn:hover {
    transform: translateY(-2px);
    box-shadow: var(--shadow-glow-blue);
    color: #fff;
}