/* ========================================
   U2C · 沉浸式多语种学习平台
   设计系统：浅深色沉浸 + 玻璃态 + 霓虹渐变（天蓝→荧光绿）
   ======================================== */

/* ---------- CSS 变量 ---------- */
:root {
    /* 浅深色基调：深蓝灰底色 + 浅色玻璃层 */
    --bg-deep: #0E1428;
    --bg-deep-2: #121A31;
    --bg-card: rgba(255, 255, 255, 0.06);
    --bg-card-hover: rgba(255, 255, 255, 0.10);
    --border-glass: rgba(255, 255, 255, 0.12);
    --border-glass-hover: rgba(255, 255, 255, 0.22);
    
    --text-primary: #EEF4FF;
    --text-secondary: #A8B6CE;
    --text-muted: #7385A0;
    --text-inverse: #0E1428;
    
    /* U2C 注册商标品牌色（仅用于商标标识本身，不参与界面配色） */
    --brand-orange: #E8822A;
    --brand-orange-dark: #C9671A;
    --brand-teal: #3BB4C4;
    --brand-teal-light: #4FC3D4;
    --brand-ink: #1A1A1A;

    /* 界面主色：天蓝 → 荧光绿 */
    --brand-sky: #87CEEB;
    --brand-lime: #5BCC00;

    --indigo-500: #87CEEB;
    --indigo-600: #6BC0E4;
    --indigo-700: #4C9DC8;
    --cyan-400: #7DE036;
    --cyan-500: #5BCC00;
    --violet-500: #a855f7;
    --pink-500: #FF2E9A;
    --emerald-500: #10b981;
    --amber-500: #FF8A00;
    --rose-500: #f43f5e;
    
    --gradient-primary: linear-gradient(135deg, #87CEEB 0%, #5BCC00 100%);
    --gradient-premium: linear-gradient(135deg, #FF8A00 0%, #FF2E9A 100%);
    --gradient-cool: linear-gradient(135deg, #5BCC00 0%, #87CEEB 100%);
    --gradient-warm: linear-gradient(135deg, #FF2E9A 0%, #a855f7 100%);
    --gradient-success: linear-gradient(135deg, #5BCC00 0%, #22d3ee 100%);
    
    --shadow-glow: 0 0 40px rgba(135, 206, 235, 0.30);
    --shadow-card: 0 8px 32px rgba(0, 0, 0, 0.32);
    --shadow-float: 0 20px 60px rgba(0, 0, 0, 0.5);
    
    --radius-sm: 8px;
    --radius-md: 14px;
    --radius-lg: 20px;
    --radius-xl: 28px;
    --radius-full: 999px;
    
    /* 标题：思源黑体 */
    --font-display: 'Noto Sans SC', 'Source Han Sans SC', 'PingFang SC', system-ui, sans-serif;
    --font-body: 'Noto Sans SC', system-ui, sans-serif;
    --font-jp: 'Noto Sans JP', 'Noto Sans SC', sans-serif;
    --font-kr: 'Noto Sans KR', 'Noto Sans SC', sans-serif;
    --font-ar: 'Noto Naskh Arabic', 'Amiri', serif;
    
    --transition-fast: 0.15s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-base: 0.25s cubic-bezier(0.4, 0, 0.2, 1);
    --transition-slow: 0.4s cubic-bezier(0.4, 0, 0.2, 1);
}

/* ---------- 基础重置 ---------- */
* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; overflow-x: hidden; }
body {
    font-family: var(--font-body);
    background-color: var(--bg-deep);
    background-image:
        radial-gradient(1100px 680px at 50% -18%, rgba(135, 206, 235, 0.16), transparent 62%),
        radial-gradient(900px 560px at 92% 8%, rgba(91, 204, 0, 0.07), transparent 60%),
        linear-gradient(180deg, #131B33 0%, #0E1428 46%, #0B1020 100%);
    background-attachment: fixed;
    color: var(--text-primary);
    line-height: 1.6;
    min-height: 100vh;
    overflow-x: hidden;
    -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; transition: color var(--transition-fast); }
button { font-family: inherit; cursor: pointer; border: none; background: none; color: inherit; }
input, textarea, select { font-family: inherit; }
img { max-width: 100%; display: block; }
::-webkit-scrollbar { width: 8px; height: 8px; }
::-webkit-scrollbar-track { background: var(--bg-deep); }
::-webkit-scrollbar-thumb { background: rgba(255,255,255,0.1); border-radius: 4px; }
::-webkit-scrollbar-thumb:hover { background: rgba(255,255,255,0.2); }

/* ---------- 背景氛围层 ---------- */
.bg-atmosphere {
    position: fixed;
    inset: 0;
    z-index: 0;
    pointer-events: none;
    overflow: hidden;
}
.orb {
    position: absolute;
    border-radius: 50%;
    filter: blur(80px);
    opacity: 0.5;
    animation: float 20s ease-in-out infinite;
}
.orb-1 {
    width: 500px; height: 500px;
    background: radial-gradient(circle, var(--indigo-600), transparent);
    top: -10%; left: -5%;
    animation-delay: 0s;
}
.orb-2 {
    width: 400px; height: 400px;
    background: radial-gradient(circle, var(--cyan-500), transparent);
    top: 40%; right: -10%;
    animation-delay: -7s;
}
.orb-3 {
    width: 350px; height: 350px;
    background: radial-gradient(circle, var(--pink-500), transparent);
    bottom: -10%; left: 30%;
    animation-delay: -14s;
}
.orb-4 {
    width: 620px; height: 620px;
    background: radial-gradient(circle, rgba(255, 255, 255, 0.55), transparent 62%);
    top: 18%; left: 42%;
    opacity: 0.16;
    filter: blur(110px);
    animation-delay: -4s;
}
@keyframes float {
    0%, 100% { transform: translate(0, 0) scale(1); }
    33% { transform: translate(50px, -30px) scale(1.1); }
    66% { transform: translate(-30px, 40px) scale(0.95); }
}
.grid-overlay {
    position: absolute;
    inset: 0;
    background-image: 
        linear-gradient(rgba(255,255,255,0.02) 1px, transparent 1px),
        linear-gradient(90deg, rgba(255,255,255,0.02) 1px, transparent 1px);
    background-size: 60px 60px;
    mask-image: radial-gradient(ellipse at center, black 30%, transparent 80%);
}

/* ---------- 测试模式标识（DEV_UNLOCK_ALL=true 时由 app.js 注入） ---------- */
.test-mode-banner {
    position: fixed;
    top: 0; left: 0; right: 0;
    z-index: 200;
    display: flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 7px 14px;
    font-size: 12.5px;
    font-weight: 600;
    letter-spacing: 0.2px;
    color: #1a1300;
    background: linear-gradient(90deg, #fbbf24, #f59e0b 55%, #fbbf24);
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.28);
    text-align: center;
}
body.test-mode { padding-top: 32px; }
body.test-mode .navbar { top: 32px; }
@media (max-width: 640px) {
    .test-mode-banner { font-size: 11px; padding: 6px 10px; gap: 6px; }
}

/* ---------- 导航栏 ---------- */
.navbar {
    position: fixed;
    top: 0; left: 0; right: 0;
    z-index: 100;
    padding: 16px 0;
    transition: all 0.35s cubic-bezier(0.4, 0, 0.2, 1);
    background: transparent;
}
.navbar.scrolled {
    background: rgba(8, 12, 28, 0.72);
    backdrop-filter: blur(24px) saturate(1.4);
    -webkit-backdrop-filter: blur(24px) saturate(1.4);
    border-bottom: 1px solid rgba(135, 206, 235, 0.12);
    padding: 10px 0;
    box-shadow: 0 8px 32px rgba(0, 0, 0, 0.22);
}
/* 滚回到最顶部时，导航栏恢复全透明 */
.navbar.at-top {
    background: transparent !important;
    backdrop-filter: none !important;
    -webkit-backdrop-filter: none !important;
    border-bottom-color: transparent;
    box-shadow: none;
}
.nav-container {
    max-width: 1400px;
    margin: 0 auto;
    padding: 0 32px;
    display: flex;
    align-items: center;
    gap: 40px;
}
.nav-logo {
    display: flex;
    align-items: center;
    gap: 12px;
    font-family: var(--font-display);
    font-weight: 700;
    font-size: 22px;
    letter-spacing: -0.5px;
}
/* U2C 商标标识（矢量文件，透明底，与页面底色一致） */
.logo-chip {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    background: transparent;
    transition: transform var(--transition-fast), filter var(--transition-fast);
}
.nav-logo:hover .logo-chip {
    transform: translateY(-1px);
    filter: drop-shadow(0 4px 12px rgba(232, 130, 42, 0.45));
}
.logo-chip-sm { height: 30px; }
.logo-mark { height: 64px; width: auto; display: block; }
.logo-chip-sm .logo-mark { height: 28px; }
.nav-links {
    display: flex;
    gap: 12px;
    flex: 1;
    justify-content: center;
}
.nav-link {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 10px 20px;
    border-radius: var(--radius-full);
    font-size: 16px;
    font-weight: 500;
    white-space: nowrap;
    color: var(--text-secondary);
    transition: all var(--transition-fast);
    position: relative;
}
.nav-link i {
    transition: transform var(--transition-fast);
}
.nav-link:hover {
    color: var(--text-primary);
    background: var(--bg-card);
    transform: translateY(-2px);
    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.25);
}
.nav-link:hover i {
    transform: scale(1.18);
}
/* 底部渐变指示条：默认隐藏，hover / 激活时从中央展开 */
.nav-link::after {
    content: '';
    position: absolute;
    bottom: 4px; left: 50%;
    transform: translateX(-50%);
    width: 0; height: 3px;
    background: var(--gradient-primary);
    border-radius: 2px;
    opacity: 0;
    transition: width 0.25s ease, opacity 0.25s ease;
}
.nav-link:hover::after,
.nav-link.active::after {
    width: 20px;
    opacity: 1;
}
.nav-link.active {
    color: var(--text-primary);
    background: var(--bg-card);
}
.nav-link-premium {
    background: linear-gradient(135deg, rgba(245,158,11,0.15), rgba(236,72,153,0.15)) !important;
    color: var(--amber-500) !important;
    border: 1px solid rgba(245,158,11,0.3);
}
.nav-link-premium:hover {
    background: linear-gradient(135deg, rgba(245,158,11,0.25), rgba(236,72,153,0.25)) !important;
}
.nav-auth { display: flex; gap: 12px; align-items: center; }

/* ---------- 导航栏语言选择器 ---------- */
.nav-lang-selector {
    position: relative;
}
.lang-trigger {
    display: flex;
    align-items: center;
    gap: 8px;
    padding: 10px 16px;
    border-radius: var(--radius-full);
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    transition: all var(--transition-fast);
    cursor: pointer;
}
.lang-trigger:hover {
    color: var(--text-primary);
    background: var(--bg-card-hover);
    border-color: var(--border-glass-hover);
}
.lang-trigger .fa-language {
    font-size: 15px;
    color: var(--brand-sky);
}
.lang-chevron {
    font-size: 11px;
    transition: transform var(--transition-fast);
}
.lang-trigger.open .lang-chevron {
    transform: rotate(180deg);
}
.lang-dropdown {
    position: absolute;
    top: calc(100% + 8px);
    right: 0;
    min-width: 200px;
    background: rgba(14, 20, 40, 0.95);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-md);
    box-shadow: var(--shadow-card), 0 0 40px rgba(135, 206, 235, 0.15);
    overflow: hidden;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-8px);
    transition: opacity var(--transition-fast), transform var(--transition-fast), visibility var(--transition-fast);
    z-index: 200;
}
.lang-dropdown.show {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
}
.lang-option {
    display: flex;
    align-items: center;
    gap: 12px;
    padding: 12px 18px;
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    cursor: pointer;
    transition: all var(--transition-fast);
    border-left: 3px solid transparent;
}
.lang-option:hover {
    background: var(--bg-card);
    color: var(--text-primary);
}
.lang-option.active {
    background: rgba(135, 206, 235, 0.12);
    color: var(--text-primary);
    border-left-color: var(--brand-sky);
}
.lang-option .lang-emoji {
    font-size: 18px;
    width: 24px;
    text-align: center;
}
.lang-option .lang-name {
    flex: 1;
}
.lang-option .lang-check {
    color: var(--brand-lime);
    opacity: 0;
    font-size: 13px;
}
.lang-option.active .lang-check {
    opacity: 1;
}

.mobile-menu-btn {
    display: none;
    width: 44px; height: 44px;
    border-radius: var(--radius-full);
    background: var(--bg-card);
    align-items: center;
    justify-content: center;
    font-size: 18px;
}

/* ---------- 按钮组件 ---------- */
.btn {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 8px;
    padding: 12px 28px;
    border-radius: var(--radius-full);
    font-weight: 600;
    font-size: 14px;
    transition: all var(--transition-base);
    cursor: pointer;
    white-space: nowrap;
}
.btn-primary {
    background: var(--gradient-primary);
    color: white;
    box-shadow: var(--shadow-glow);
}
.btn-primary:hover {
    transform: translateY(-2px);
    box-shadow: 0 10px 40px rgba(99, 102, 241, 0.4);
}
.btn-ghost {
    background: var(--bg-card);
    color: var(--text-primary);
    border: 1px solid var(--border-glass);
}
.btn-ghost:hover {
    background: var(--bg-card-hover);
    border-color: var(--border-glass-hover);
}
.btn-premium {
    background: var(--gradient-premium);
    color: white;
    box-shadow: 0 10px 30px rgba(245, 158, 11, 0.3);
}
.btn-premium:hover {
    transform: translateY(-2px);
    box-shadow: 0 15px 40px rgba(245, 158, 11, 0.4);
}
.btn-danger {
    background: linear-gradient(135deg, #ef4444, #dc2626);
    color: white;
    box-shadow: 0 10px 30px rgba(239, 68, 68, 0.3);
}
.btn-danger:hover {
    transform: translateY(-2px);
    box-shadow: 0 15px 40px rgba(239, 68, 68, 0.4);
}
.btn-outline {
    background: transparent;
    color: var(--text-primary);
    border: 2px solid var(--border-glass-hover);
}
.btn-outline:hover {
    border-color: var(--indigo-500);
    background: rgba(99, 102, 241, 0.1);
}
.btn-sm { padding: 8px 18px; font-size: 13px; }
.btn-lg { padding: 16px 36px; font-size: 16px; }

/* ---------- 主内容区 ---------- */
#app {
    position: relative;
    z-index: 1;
    padding-top: 100px;
    min-height: calc(100vh - 100px);
    /* 防止子元素（如悬浮卡片负偏移、亚像素取整）造成横向亚像素溢出 */
    overflow-x: clip;
}

/* ---------- Hero 区域 ---------- */
.hero {
    max-width: 1400px;
    margin: 0 auto;
    padding: 60px 32px 80px;
    display: grid;
    grid-template-columns: 1.1fr 1fr;
    gap: 60px;
    align-items: center;
}
.hero-content { animation: heroFadeUp 0.9s cubic-bezier(0.16, 1, 0.3, 1); }
@keyframes heroFadeUp {
    0% { opacity: 0; transform: translateY(40px) scale(0.98); }
    100% { opacity: 1; transform: translateY(0) scale(1); }
}
@keyframes fadeUp {
    from { opacity: 0; transform: translateY(30px); }
    to { opacity: 1; transform: translateY(0); }
}
.hero-badge {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 8px 16px;
    border-radius: var(--radius-full);
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    font-size: 13px;
    color: var(--cyan-400);
    margin-bottom: 24px;
}
.hero-badge .pulse {
    width: 8px; height: 8px;
    background: var(--emerald-500);
    border-radius: 50%;
    animation: pulse 2s infinite;
}
@keyframes pulse {
    0%, 100% { opacity: 1; }
    50% { opacity: 0.4; }
}
.hero-title {
    font-family: var(--font-display);
    font-size: 24px;
    font-weight: 700;
    line-height: 1.3;
    letter-spacing: -0.5px;
    margin-bottom: 24px;
}
.hero-title .hero-lead {
    display: block;
    font-size: 52px;
    font-weight: 700;
    line-height: 1.2;
    letter-spacing: -1.5px;
    color: var(--text-primary);
    margin-bottom: 16px;
}
.hero-title .hero-langs {
    display: block;
    font-size: 44px;
    font-weight: 700;
    line-height: 1.4;
    letter-spacing: -1.5px;
    word-spacing: -1px;
    white-space: nowrap;
}
.hero-title .gradient-text {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.hero-title .en-text { color: #3b82f6; }
.hero-title .fr-text { color: #818cf8; }
.hero-title .es-text { color: #f59e0b; }
.hero-title .pt-text { color: #10b981; }
.hero-title .jp-text { font-family: var(--font-jp); color: var(--cyan-400); }
.hero-title .kr-text { font-family: var(--font-kr); color: var(--violet-500); }
.hero-title .ar-text { font-family: var(--font-ar); direction: rtl; unicode-bidi: isolate; color: #14b8a6; }
/* 阿拉伯语通用字体与 RTL：覆盖单词、语法题、选项、口语、听力输入与原文等所有 ar 容器 */
.ar,
.word-main.ar,
.speak-display.ar,
.quiz-question.ar,
.quiz-question .ar,
.listen-text-input.ar,
.chat-bubble.ar,
.lang-name.ar,
.post-item[data-lang="ar"] .post-content {
    font-family: var(--font-ar);
    direction: rtl;
    unicode-bidi: isolate;
}
.hero-subtitle {
    font-size: 18px;
    color: var(--text-secondary);
    line-height: 1.7;
    margin-bottom: 36px;
    max-width: 540px;
}
.hero-actions { display: flex; gap: 16px; flex-wrap: wrap; }
.hero-stats {
    display: flex;
    gap: 40px;
    margin-top: 48px;
    padding-top: 32px;
    border-top: 1px solid var(--border-glass);
}
.hero-stat-num {
    font-family: var(--font-display);
    font-size: 32px;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.hero-stat-label {
    font-size: 13px;
    color: var(--text-muted);
    margin-top: 4px;
}

/* 首页 · 每日一句 */
.daily-sentence {
    margin-top: 28px;
    padding: 18px 22px;
    border-radius: var(--radius-lg);
    background: rgba(135, 206, 235, 0.08);
    border: 1px solid rgba(135, 206, 235, 0.22);
    max-width: 520px;
}
.daily-label {
    display: flex;
    align-items: center;
    gap: 8px;
    font-size: 12px;
    letter-spacing: 0.08em;
    color: var(--text-muted);
}
.daily-label i { color: #87CEEB; font-size: 11px; }
.daily-text {
    margin-top: 10px;
    font-size: 17px;
    font-weight: 500;
    line-height: 1.6;
    color: var(--text-primary);
}
.daily-translation {
    margin-top: 6px;
    font-size: 13px;
    line-height: 1.6;
    color: var(--text-secondary);
}

/* Hero 视觉演示区 */
.hero-visual {
    position: relative;
    height: 560px;
    animation: heroFadeUp 1s cubic-bezier(0.16, 1, 0.3, 1) 0.15s both;
}
@keyframes heroFloatY {
    0%, 100% { transform: translateY(0); }
    50% { transform: translateY(-14px); }
}
.visual-card {
    position: absolute;
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    box-shadow: var(--shadow-float);
    transition: all var(--transition-slow);
    animation: heroFloatY 6s ease-in-out infinite;
}
.visual-card:nth-child(1) { animation-delay: 0s; }
.visual-card:nth-child(2) { animation-delay: -2s; animation-duration: 7s; }
.visual-card:nth-child(3) { animation-delay: -4s; animation-duration: 8s; }
.vc-chat {
    top: 0; left: 0; right: 0;
    padding: 24px;
}
.vc-chat-header {
    display: flex; align-items: center; gap: 12px;
    margin-bottom: 16px;
}
.vc-avatar {
    width: 40px; height: 40px; border-radius: 50%;
    background: var(--gradient-primary);
    display: flex; align-items: center; justify-content: center;
    font-size: 16px; font-weight: 700;
}
.vc-name { font-weight: 600; font-size: 14px; }
.vc-role { font-size: 12px; color: var(--text-muted); }
.chat-bubble {
    padding: 12px 16px;
    border-radius: 16px;
    font-size: 14px;
    margin-bottom: 10px;
    max-width: 85%;
}
.chat-bubble.bot {
    background: rgba(135,206,235,0.15);
    border: 1px solid rgba(135,206,235,0.25);
    border-top-left-radius: 4px;
}
.chat-bubble.user {
    background: rgba(91,204,0,0.15);
    border: 1px solid rgba(91,204,0,0.25);
    border-top-right-radius: 4px;
    margin-left: auto;
}
.chat-bubble.jp { font-family: var(--font-jp); }
.chat-bubble.kr { font-family: var(--font-kr); }

.vc-progress {
    bottom: 0; right: 0; width: 260px;
    padding: 20px;
}
.progress-ring-wrap {
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 12px;
}
.progress-ring {
    width: 100px; height: 100px;
}
.progress-ring circle {
    fill: none;
    stroke-width: 8;
    stroke-linecap: round;
}
.progress-ring .bg { stroke: var(--border-glass); }
.progress-ring .fg {
    stroke: url(#lg1);
    stroke-dasharray: 283;
    stroke-dashoffset: 56;
    transform: rotate(-90deg);
    transform-origin: center;
}
.progress-pct {
    font-family: var(--font-display);
    font-size: 24px;
    font-weight: 700;
}
.progress-label { font-size: 13px; color: var(--text-muted); }

.vc-lang {
    bottom: 60px; left: -20px;
    padding: 16px 20px;
    display: flex; align-items: center; gap: 14px;
}
.lang-flag { font-size: 28px; }
.lang-info { font-size: 13px; }
.lang-info .name { font-weight: 600; }
.lang-info .level { color: var(--text-muted); }

/* ---------- 通用 Section 样式 ---------- */
.section {
    max-width: 1400px;
    margin: 0 auto;
    padding: 80px 32px;
}
.section-header {
    text-align: center;
    margin-bottom: 56px;
}
.section-eyebrow {
    display: inline-block;
    font-family: var(--font-display);
    font-size: 13px;
    font-weight: 600;
    letter-spacing: 2px;
    text-transform: uppercase;
    color: var(--cyan-400);
    margin-bottom: 12px;
}
.section-title {
    font-family: var(--font-display);
    font-size: 44px;
    font-weight: 700;
    letter-spacing: -1px;
    margin-bottom: 16px;
}
.section-desc {
    font-size: 17px;
    color: var(--text-secondary);
    max-width: 600px;
    margin: 0 auto;
}

/* ---------- 功能特性网格 ---------- */
.features-grid {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 24px;
}
.feature-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 36px 28px;
    transition: all var(--transition-base);
    position: relative;
    overflow: hidden;
}
.feature-card::before {
    content: '';
    position: absolute;
    inset: 0;
    background: var(--gradient-primary);
    opacity: 0;
    transition: opacity var(--transition-base);
    z-index: 0;
}
.feature-card:hover {
    transform: translateY(-4px);
    border-color: var(--border-glass-hover);
}
.feature-card:hover::before { opacity: 0.03; }
.feature-icon {
    width: 56px; height: 56px;
    border-radius: var(--radius-md);
    display: flex; align-items: center; justify-content: center;
    font-size: 24px;
    margin-bottom: 20px;
    position: relative;
    z-index: 1;
}
.feature-icon.gradient-1 { background: linear-gradient(135deg, rgba(135,206,235,0.2), rgba(135,206,235,0.05)); color: var(--indigo-500); }
.feature-icon.gradient-2 { background: linear-gradient(135deg, rgba(91,204,0,0.2), rgba(91,204,0,0.05)); color: var(--cyan-400); }
.feature-icon.gradient-3 { background: linear-gradient(135deg, rgba(168,85,247,0.2), rgba(168,85,247,0.05)); color: var(--violet-500); }
.feature-icon.gradient-4 { background: linear-gradient(135deg, rgba(16,185,129,0.2), rgba(16,185,129,0.05)); color: var(--emerald-500); }
.feature-icon.gradient-5 { background: linear-gradient(135deg, rgba(245,158,11,0.2), rgba(245,158,11,0.05)); color: var(--amber-500); }
.feature-icon.gradient-6 { background: linear-gradient(135deg, rgba(236,72,153,0.2), rgba(236,72,153,0.05)); color: var(--pink-500); }
.feature-title {
    font-family: var(--font-display);
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 12px;
    position: relative; z-index: 1;
}
.feature-desc {
    font-size: 14px;
    color: var(--text-secondary);
    line-height: 1.7;
    position: relative; z-index: 1;
}

/* ---------- 语言选择卡片 ---------- */
.lang-showcase {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 32px;
}
.lang-card {
    position: relative;
    border-radius: var(--radius-xl);
    padding: 48px 36px;
    overflow: hidden;
    cursor: pointer;
    transition: all 0.5s cubic-bezier(0.16, 1, 0.3, 1);
    border: 1px solid var(--border-glass);
    background: var(--bg-card);
}
.lang-card::before {
    content: '';
    position: absolute;
    inset: 0;
    opacity: 0.6;
    transition: opacity 0.5s ease;
}
/* 所有卡片的默认光晕色 */
.lang-card::after {
    content: '';
    position: absolute;
    inset: -2px;
    border-radius: inherit;
    opacity: 0;
    background: radial-gradient(circle at var(--glow-x, 50%) var(--glow-y, 50%), var(--glow-color, rgba(135,206,235,0.55)), transparent 60%);
    filter: blur(30px);
    transition: opacity 0.5s ease;
    pointer-events: none;
    z-index: 0;
}
.lang-card.lang-en::before { background: linear-gradient(135deg, rgba(135,206,235,0.2), rgba(91,204,0,0.2)); }
.lang-card.lang-en { --glow-color: rgba(135,206,235,0.45); }
.lang-card.lang-ja::before { background: linear-gradient(135deg, rgba(244,63,94,0.2), rgba(168,85,247,0.2)); }
.lang-card.lang-ja { --glow-color: rgba(244,63,94,0.42); }
.lang-card.lang-ko::before { background: linear-gradient(135deg, rgba(16,185,129,0.2), rgba(91,204,0,0.2)); }
.lang-card.lang-ko { --glow-color: rgba(16,185,129,0.45); }
/* 其他语言（通用渐变光晕） */
.lang-card.lang-fr { --glow-color: rgba(139, 92, 246, 0.42); }
.lang-card.lang-es { --glow-color: rgba(245, 158, 11, 0.42); }
.lang-card.lang-pt { --glow-color: rgba(16, 185, 129, 0.42); }
.lang-card.lang-ar { --glow-color: rgba(20, 184, 166, 0.42); }

.lang-card:hover {
    transform: translateY(-10px);
    border-color: rgba(255, 255, 255, 0.22);
    box-shadow: 0 24px 64px rgba(0, 0, 0, 0.35), 0 0 40px var(--glow-color, rgba(135,206,235,0.3));
}
.lang-card:hover::before { opacity: 0.9; }
.lang-card:hover::after { opacity: 1; }
.lang-card-content { position: relative; z-index: 1; }
.lang-emoji { font-size: 48px; margin-bottom: 20px; }
.lang-name {
    font-family: var(--font-display);
    font-size: 32px;
    font-weight: 700;
    margin-bottom: 8px;
}
.lang-name.jp { font-family: var(--font-jp); }
.lang-name.kr { font-family: var(--font-kr); }
.lang-meta {
    font-size: 14px;
    color: var(--text-secondary);
    margin-bottom: 24px;
}
.lang-tags {
    display: flex; gap: 8px; flex-wrap: wrap;
}
.lang-tag {
    padding: 6px 12px;
    border-radius: var(--radius-full);
    font-size: 12px;
    background: rgba(255,255,255,0.1);
    border: 1px solid rgba(255,255,255,0.15);
}

/* ---------- 课程卡片 ---------- */
.courses-filter {
    display: flex;
    gap: 12px;
    justify-content: center;
    margin-bottom: 40px;
    flex-wrap: wrap;
}
.filter-btn {
    padding: 10px 24px;
    border-radius: var(--radius-full);
    font-size: 14px;
    font-weight: 500;
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    color: var(--text-secondary);
    transition: all var(--transition-fast);
}
.filter-btn:hover, .filter-btn.active {
    background: var(--gradient-primary);
    color: white;
    border-color: transparent;
}
.course-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(320px, 1fr));
    gap: 24px;
}
.course-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    overflow: hidden;
    transition: all var(--transition-base);
    cursor: pointer;
}
.course-card:hover {
    transform: translateY(-4px);
    border-color: var(--border-glass-hover);
    box-shadow: var(--shadow-float);
}
.course-cover {
    height: 160px;
    position: relative;
    display: flex;
    align-items: center;
    justify-content: center;
    font-size: 56px;
}
.course-cover.en { background: linear-gradient(135deg, var(--indigo-600), var(--cyan-500)); }
.course-cover.ja { background: linear-gradient(135deg, var(--rose-500), var(--violet-500)); }
.course-cover.ko { background: linear-gradient(135deg, var(--emerald-500), var(--cyan-400)); }
.course-level {
    position: absolute;
    top: 12px; left: 12px;
    padding: 4px 12px;
    border-radius: var(--radius-full);
    background: rgba(0,0,0,0.4);
    backdrop-filter: blur(10px);
    font-size: 12px;
    font-weight: 600;
}
.course-premium-badge {
    position: absolute;
    top: 12px; right: 12px;
    padding: 4px 12px;
    border-radius: var(--radius-full);
    background: var(--gradient-premium);
    font-size: 11px;
    font-weight: 700;
    color: white;
}
.course-pro-badge { background: var(--gradient-primary); }
.course-info { padding: 24px; }
.course-title {
    font-family: var(--font-display);
    font-size: 18px;
    font-weight: 600;
    margin-bottom: 8px;
}
.course-desc {
    font-size: 13px;
    color: var(--text-secondary);
    line-height: 1.6;
    margin-bottom: 16px;
}
.course-meta {
    display: flex;
    gap: 16px;
    font-size: 12px;
    color: var(--text-muted);
}
.course-meta i { margin-right: 4px; }

/* ---------- 学习模块页面 ---------- */
.learn-page { padding-top: 20px; }
.learn-nav-tabs {
    display: flex;
    gap: 8px;
    margin-bottom: 32px;
    overflow-x: auto;
    padding-bottom: 8px;
}
.learn-tab {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 14px 24px;
    border-radius: var(--radius-md);
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    font-size: 14px;
    font-weight: 500;
    color: var(--text-secondary);
    white-space: nowrap;
    transition: all var(--transition-fast);
}
.learn-tab:hover { color: var(--text-primary); }
.learn-tab.active {
    background: var(--gradient-primary);
    color: white;
    border-color: transparent;
}

/* 单词卡片翻转 */
.word-card-container {
    perspective: 1000px;
    margin-bottom: 32px;
}
.word-card {
    width: 100%;
    height: 280px;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.6s cubic-bezier(0.4, 0, 0.2, 1);
    cursor: pointer;
}
.word-card.flipped { transform: rotateY(180deg); }
.word-face {
    position: absolute;
    inset: 0;
    backface-visibility: hidden;
    border-radius: var(--radius-lg);
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    display: flex;
    flex-direction: column;
    align-items: center;
    justify-content: center;
    padding: 32px;
}
.word-face.back {
    transform: rotateY(180deg);
    background: linear-gradient(135deg, rgba(135,206,235,0.15), rgba(91,204,0,0.15));
}
.word-main {
    font-family: var(--font-display);
    font-size: 56px;
    font-weight: 700;
    margin-bottom: 16px;
}
.word-main.jp { font-family: var(--font-jp); }
.word-main.kr { font-family: var(--font-kr); }
.word-phonetic { font-size: 18px; color: var(--text-secondary); margin-bottom: 24px; }
.word-meaning {
    font-size: 24px;
    font-weight: 600;
    margin-bottom: 12px;
}
.word-example {
    font-size: 14px;
    color: var(--text-secondary);
    text-align: center;
    font-style: italic;
}
.word-actions {
    display: flex;
    gap: 12px;
    justify-content: center;
}
.word-stat {
    display: flex;
    gap: 24px;
    justify-content: center;
    margin-bottom: 24px;
}
.word-stat-item {
    text-align: center;
}
.word-stat-num {
    font-family: var(--font-display);
    font-size: 28px;
    font-weight: 700;
    color: var(--cyan-400);
}
.word-stat-label { font-size: 12px; color: var(--text-muted); }

/* 语法练习 */
.grammar-quiz {
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 40px;
}
.quiz-question {
    font-size: 20px;
    font-weight: 600;
    margin-bottom: 32px;
    line-height: 1.7;
}
.quiz-options { display: flex; flex-direction: column; gap: 12px; }
.quiz-option {
    padding: 18px 24px;
    border-radius: var(--radius-md);
    background: rgba(255,255,255,0.03);
    border: 1px solid var(--border-glass);
    text-align: left;
    font-size: 15px;
    transition: all var(--transition-fast);
    display: flex; align-items: center; gap: 14px;
}
.quiz-option:hover:not(.disabled) {
    background: rgba(135,206,235,0.1);
    border-color: var(--indigo-500);
}
.quiz-option.selected {
    background: rgba(135,206,235,0.15);
    border-color: var(--indigo-500);
}
.quiz-option.correct {
    background: rgba(16,185,129,0.15);
    border-color: var(--emerald-500);
    color: var(--emerald-500);
}
.quiz-option.wrong {
    background: rgba(244,63,94,0.15);
    border-color: var(--rose-500);
    color: var(--rose-500);
}
.quiz-option .opt-letter {
    width: 32px; height: 32px;
    border-radius: 50%;
    background: rgba(255,255,255,0.1);
    display: flex; align-items: center; justify-content: center;
    font-weight: 600; font-size: 14px;
    flex-shrink: 0;
}
.quiz-option.correct .opt-letter { background: var(--emerald-500); }
.quiz-option.wrong .opt-letter { background: var(--rose-500); }
.grammar-jp .quiz-option .opt-letter { font-family: var(--font-jp); }

/* 口语跟读 */
.speaking-practice {
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 40px;
    text-align: center;
}
.speak-display {
    font-family: var(--font-display);
    font-size: 32px;
    font-weight: 600;
    padding: 40px 24px;
    background: rgba(0,0,0,0.3);
    border-radius: var(--radius-md);
    margin-bottom: 24px;
    border: 1px solid var(--border-glass);
}
.speak-display.jp { font-family: var(--font-jp); }
.speak-display.kr { font-family: var(--font-kr); }
.speak-controls {
    display: flex;
    gap: 16px;
    justify-content: center;
    margin-bottom: 24px;
}
.speak-btn {
    width: 80px; height: 80px;
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    font-size: 28px;
    transition: all var(--transition-base);
}
.speak-btn.play { background: var(--gradient-primary); }
.speak-btn.record { background: var(--gradient-warm); }
.speak-btn.record.recording {
    animation: recording-pulse 1s infinite;
}
@keyframes recording-pulse {
    0%, 100% { box-shadow: 0 0 0 0 rgba(244,63,94,0.6); }
    50% { box-shadow: 0 0 0 20px rgba(244,63,94,0); }
}
.speak-result {
    padding: 16px 24px;
    border-radius: var(--radius-md);
    background: rgba(91,204,0,0.1);
    border: 1px solid rgba(91,204,0,0.2);
    display: none;
}
.speak-result.show { display: block; animation: fadeUp 0.3s ease-out; }
.speak-score {
    font-family: var(--font-display);
    font-size: 48px;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}

/* 听力训练 */
.listening-practice {
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 40px;
}
.listen-audio {
    display: flex;
    align-items: center;
    gap: 20px;
    padding: 24px;
    background: rgba(0,0,0,0.3);
    border-radius: var(--radius-md);
    margin-bottom: 32px;
}
.listen-play-btn {
    width: 60px; height: 60px;
    border-radius: 50%;
    background: var(--gradient-primary);
    display: flex; align-items: center; justify-content: center;
    font-size: 20px;
    flex-shrink: 0;
}
.listen-wave {
    flex: 1;
    display: flex;
    gap: 3px;
    height: 40px;
    align-items: center;
}
.wave-bar {
    flex: 1;
    background: linear-gradient(to top, var(--indigo-500), var(--cyan-400));
    border-radius: 2px;
    opacity: 0.4;
    transition: all 0.15s;
}
.wave-bar.playing { opacity: 1; animation: wave 1.2s ease-in-out infinite; }
@keyframes wave {
    0%, 100% { height: 20%; }
    50% { height: 100%; }
}
.listen-text-input {
    width: 100%;
    padding: 16px 20px;
    border-radius: var(--radius-md);
    background: rgba(0,0,0,0.3);
    border: 1px solid var(--border-glass);
    color: var(--text-primary);
    font-size: 16px;
    outline: none;
    transition: border-color var(--transition-fast);
}
.listen-text-input:focus { border-color: var(--indigo-500); }

/* ---------- 进度页面 ---------- */
.progress-overview {
    display: grid;
    grid-template-columns: repeat(4, 1fr);
    gap: 20px;
    margin-bottom: 40px;
}
.progress-stat-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 28px;
}
.progress-stat-icon {
    width: 44px; height: 44px;
    border-radius: var(--radius-md);
    display: flex; align-items: center; justify-content: center;
    font-size: 20px;
    margin-bottom: 16px;
}
.progress-stat-num {
    font-family: var(--font-display);
    font-size: 36px;
    font-weight: 700;
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.progress-stat-label { font-size: 13px; color: var(--text-muted); margin-top: 4px; }

.progress-main-grid {
    display: grid;
    grid-template-columns: 2fr 1fr;
    gap: 24px;
    margin-bottom: 40px;
}
.chart-card, .streak-card, .achievements-card, .recommend-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 32px;
}
.card-header {
    display: flex;
    align-items: center;
    justify-content: space-between;
    margin-bottom: 24px;
}
.card-title {
    font-family: var(--font-display);
    font-size: 18px;
    font-weight: 600;
}
.chart-container { height: 280px; }
.bar-chart {
    display: flex;
    align-items: flex-end;
    justify-content: space-between;
    height: 100%;
    gap: 12px;
}
.bar-item {
    flex: 1;
    display: flex;
    flex-direction: column;
    align-items: center;
    gap: 8px;
    height: 100%;
    justify-content: flex-end;
}
.bar {
    width: 100%;
    background: var(--gradient-primary);
    border-radius: 6px 6px 0 0;
    transition: height var(--transition-slow);
    position: relative;
}
.bar:hover { filter: brightness(1.2); }
.bar-label { font-size: 11px; color: var(--text-muted); }

.streak-display {
    text-align: center;
    padding: 32px 0;
}
.streak-num {
    font-family: var(--font-display);
    font-size: 72px;
    font-weight: 700;
    background: var(--gradient-warm);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
    line-height: 1;
}
.streak-unit {
    font-family: var(--font-display);
    font-size: 24px;
    color: var(--text-secondary);
    margin-left: 8px;
}
.streak-desc { font-size: 14px; color: var(--text-muted); margin-top: 12px; }
.streak-calendar {
    display: grid;
    grid-template-columns: repeat(7, 1fr);
    gap: 4px;
    margin-top: 24px;
}
.cal-day {
    aspect-ratio: 1;
    border-radius: 4px;
    background: rgba(255,255,255,0.05);
    display: flex; align-items: center; justify-content: center;
    font-size: 11px;
}
.cal-day.active {
    background: var(--gradient-primary);
    color: white;
}
.cal-day.today {
    border: 2px solid var(--amber-500);
}

/* ---------- 会员页面 ---------- */
.membership-hero {
    text-align: center;
    padding: 60px 32px 40px;
    max-width: 800px;
    margin: 0 auto;
}
.membership-hero h1 {
    font-family: var(--font-display);
    font-size: 52px;
    font-weight: 700;
    letter-spacing: -1px;
    margin-bottom: 16px;
}
.membership-hero h1 .gold-text {
    background: linear-gradient(135deg, #FF8A00, #FF2E9A);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.membership-plans {
    display: grid;
    grid-template-columns: repeat(3, 1fr);
    gap: 28px;
    padding: 40px 32px;
    max-width: 1200px;
    margin: 0 auto;
}
.plan-card {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-xl);
    padding: 40px 32px;
    transition: all var(--transition-base);
    position: relative;
}
.plan-card:hover { transform: translateY(-4px); }
.plan-card.featured {
    background: linear-gradient(180deg, rgba(245,158,11,0.08), rgba(236,72,153,0.08));
    border-color: rgba(245,158,11,0.4);
    box-shadow: 0 0 60px rgba(245,158,11,0.15);
}
.plan-badge {
    position: absolute;
    top: -14px; left: 50%;
    transform: translateX(-50%);
    padding: 6px 18px;
    border-radius: var(--radius-full);
    background: var(--gradient-premium);
    font-size: 12px;
    font-weight: 700;
    color: white;
}
.plan-name {
    font-family: var(--font-display);
    font-size: 22px;
    font-weight: 700;
    margin-bottom: 8px;
}
.plan-desc { font-size: 13px; color: var(--text-muted); margin-bottom: 24px; }
.plan-price {
    font-family: var(--font-display);
    font-size: 48px;
    font-weight: 700;
    margin-bottom: 4px;
}
.plan-price .currency { font-size: 20px; }
.plan-price .period { font-size: 14px; color: var(--text-muted); font-weight: 400; }
.plan-features {
    list-style: none;
    margin: 28px 0;
    display: flex; flex-direction: column; gap: 14px;
}
.plan-features li {
    display: flex; align-items: center; gap: 12px;
    font-size: 14px;
}
.plan-features li i.check { color: var(--emerald-500); }
.plan-features li i.cross { color: var(--text-muted); }
.plan-features li.included { color: var(--text-primary); }
.plan-features li.excluded { color: var(--text-muted); }

/* ---------- 社区页面 ---------- */
.community-layout {
    display: grid;
    grid-template-columns: 1fr 320px;
    gap: 24px;
    max-width: 1400px;
    margin: 0 auto;
    padding: 40px 32px;
}
.post-composer {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 24px;
    margin-bottom: 24px;
}
.composer-header {
    display: flex; align-items: center; gap: 12px;
    margin-bottom: 16px;
}
.composer-avatar {
    width: 44px; height: 44px; border-radius: 50%;
    background: var(--gradient-primary);
    display: flex; align-items: center; justify-content: center;
    font-weight: 700;
}
.composer-textarea {
    width: 100%;
    min-height: 100px;
    padding: 16px;
    border-radius: var(--radius-md);
    background: rgba(0,0,0,0.3);
    border: 1px solid var(--border-glass);
    color: var(--text-primary);
    font-size: 14px;
    resize: vertical;
    outline: none;
}
.composer-textarea:focus { border-color: var(--indigo-500); }
.composer-footer {
    display: flex;
    justify-content: space-between;
    align-items: center;
    margin-top: 16px;
}
.composer-lang-picker {
    display: flex; gap: 8px;
}
.lang-chip {
    padding: 6px 14px;
    border-radius: var(--radius-full);
    font-size: 12px;
    background: rgba(255,255,255,0.05);
    border: 1px solid var(--border-glass);
    cursor: pointer;
    transition: all var(--transition-fast);
}
.lang-chip.active { background: var(--gradient-primary); border-color: transparent; }

.post-item {
    background: var(--bg-card);
    backdrop-filter: blur(10px);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 24px;
    margin-bottom: 16px;
}
.post-header {
    display: flex;
    align-items: center;
    gap: 14px;
    margin-bottom: 16px;
}
.post-avatar {
    width: 44px; height: 44px; border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    font-weight: 700; font-size: 16px;
}
.post-author-name { font-weight: 600; }
.post-meta { font-size: 12px; color: var(--text-muted); }
.post-content {
    font-size: 15px;
    line-height: 1.7;
    color: var(--text-primary);
    margin-bottom: 16px;
}
.post-footer {
    display: flex;
    gap: 24px;
    padding-top: 16px;
    border-top: 1px solid var(--border-glass);
}
.post-action {
    display: flex; align-items: center; gap: 8px;
    font-size: 13px;
    color: var(--text-muted);
    cursor: pointer;
    transition: color var(--transition-fast);
}
.post-action:hover { color: var(--indigo-500); }
.post-action.liked { color: var(--rose-500); }

/* 成就徽章 */
.achievements-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(100px, 1fr));
    gap: 16px;
}
.achievement-item {
    text-align: center;
    padding: 16px 8px;
    border-radius: var(--radius-md);
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    transition: all var(--transition-fast);
}
.achievement-item:hover { transform: translateY(-2px); border-color: var(--border-glass-hover); }
.achievement-item.locked { opacity: 0.4; }
.achievement-icon {
    width: 56px; height: 56px;
    margin: 0 auto 10px;
    border-radius: 50%;
    display: flex; align-items: center; justify-content: center;
    font-size: 24px;
}
.achievement-icon.gold { background: linear-gradient(135deg, #fbbf24, #d97706); }
.achievement-icon.silver { background: linear-gradient(135deg, #94a3b8, #64748b); }
.achievement-icon.bronze { background: linear-gradient(135deg, #d97706, #92400e); }
.achievement-name { font-size: 11px; font-weight: 600; }

/* ---------- 模态框 ---------- */
.modal-overlay {
    position: fixed;
    inset: 0;
    background: rgba(0,0,0,0.7);
    backdrop-filter: blur(8px);
    display: none;
    align-items: center;
    justify-content: center;
    z-index: 200;
    padding: 20px;
}
.modal-overlay.show { display: flex; animation: fadeIn 0.2s ease-out; }
@keyframes fadeIn { from { opacity: 0; } to { opacity: 1; } }
.modal-container {
    background: var(--bg-deep);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-xl);
    max-width: 480px;
    width: 100%;
    position: relative;
    animation: modalSlide 0.3s ease-out;
    max-height: 90vh;
    overflow-y: auto;
}
@keyframes modalSlide {
    from { opacity: 0; transform: translateY(20px) scale(0.96); }
    to { opacity: 1; transform: translateY(0) scale(1); }
}
.modal-close {
    position: absolute;
    top: 16px; right: 16px;
    width: 36px; height: 36px;
    border-radius: 50%;
    background: var(--bg-card);
    display: flex; align-items: center; justify-content: center;
    font-size: 16px;
    z-index: 2;
}
.modal-content { padding: 40px; }

/* Auth 表单 */
.auth-title {
    font-family: var(--font-display);
    font-size: 28px;
    font-weight: 700;
    margin-bottom: 8px;
}
.auth-subtitle {
    font-size: 14px;
    color: var(--text-secondary);
    margin-bottom: 28px;
}
.form-group { margin-bottom: 18px; }
.form-label {
    display: block;
    font-size: 13px;
    font-weight: 500;
    margin-bottom: 8px;
    color: var(--text-secondary);
}
.form-input {
    width: 100%;
    padding: 14px 18px;
    border-radius: var(--radius-md);
    background: rgba(0,0,0,0.3);
    border: 1px solid var(--border-glass);
    color: var(--text-primary);
    font-size: 14px;
    outline: none;
    transition: border-color var(--transition-fast);
}
.form-input:focus { border-color: var(--indigo-500); }
.form-input::placeholder { color: var(--text-muted); }
.form-error {
    font-size: 12px;
    color: var(--rose-500);
    margin-top: 6px;
    display: none;
}
.form-error.show { display: block; }
.auth-switch {
    text-align: center;
    font-size: 14px;
    color: var(--text-muted);
    margin-top: 20px;
}
.auth-switch a {
    color: var(--indigo-500);
    font-weight: 600;
}
.auth-switch a:hover { text-decoration: underline; }
.social-login {
    display: flex;
    gap: 12px;
    margin-top: 20px;
}
.social-btn {
    flex: 1;
    padding: 12px;
    border-radius: var(--radius-md);
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    display: flex; align-items: center; justify-content: center;
    gap: 8px;
    font-size: 13px;
    transition: all var(--transition-fast);
}
.social-btn:hover { background: var(--bg-card-hover); }

/* ---------- Toast 通知 ---------- */
.toast-container {
    position: fixed;
    top: 100px;
    right: 24px;
    z-index: 300;
    display: flex;
    flex-direction: column;
    gap: 12px;
}
.toast {
    padding: 16px 24px;
    border-radius: var(--radius-md);
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
    box-shadow: var(--shadow-float);
    display: flex;
    align-items: center;
    gap: 12px;
    min-width: 300px;
    animation: toastIn 0.3s ease-out;
}
@keyframes toastIn {
    from { opacity: 0; transform: translateX(100px); }
    to { opacity: 1; transform: translateX(0); }
}
.toast.success { border-left: 4px solid var(--emerald-500); }
.toast.error { border-left: 4px solid var(--rose-500); }
.toast.info { border-left: 4px solid var(--cyan-400); }
.toast.warning { border-left: 4px solid var(--amber-500); }
.toast-icon { font-size: 18px; }
.toast.success .toast-icon { color: var(--emerald-500); }
.toast.error .toast-icon { color: var(--rose-500); }
.toast.info .toast-icon { color: var(--cyan-400); }
.toast.warning .toast-icon { color: var(--amber-500); }

/* ---------- 页脚 ---------- */
.footer {
    position: relative;
    z-index: 1;
    padding: 60px 32px 24px;
    border-top: 1px solid var(--border-glass);
    background: rgba(14, 20, 40, 0.6);
    backdrop-filter: blur(20px);
}
.footer-inner {
    max-width: 1400px;
    margin: 0 auto;
    display: grid;
    grid-template-columns: 2fr 1fr 1fr 1fr;
    gap: 48px;
    margin-bottom: 40px;
}
.footer-brand {
    display: flex;
    flex-direction: column;
    gap: 16px;
}
.footer-brand-head {
    display: flex;
    align-items: center;
    gap: 12px;
}
.footer-brand-text {
    display: inline-flex;
    flex-direction: column;
    gap: 6px;
}
.footer-logo {
    width: 36px;
    height: 36px;
    border-radius: 10px;
    background: rgba(255, 255, 255, 0.06);
    padding: 4px;
}
.footer-brand-name {
    display: block;
    font-family: var(--font-display);
    font-size: 20px;
    font-weight: 700;
    letter-spacing: -0.3px;
    color: var(--text-primary);
    white-space: nowrap;
    line-height: 1.2;
}
.footer-tagline {
    display: block;
    font-size: 13px;
    line-height: 1.3;
    color: var(--text-secondary);
    /* 两端对齐：与上一行品牌名左右边缘严格对齐 */
    text-align: justify;
    text-align-last: justify;
    text-justify: inter-character;
}
.footer-links-group h4 {
    font-family: var(--font-display);
    font-size: 15px;
    font-weight: 600;
    margin-bottom: 16px;
    color: var(--text-primary);
}
.footer-links-group a {
    display: block;
    font-size: 14px;
    color: var(--text-muted);
    padding: 5px 0;
    transition: color var(--transition-fast);
}
.footer-links-group a:hover { color: var(--indigo-500); }
.footer-bottom {
    max-width: 1400px;
    margin: 0 auto;
    padding-top: 24px;
    border-top: 1px solid var(--border-glass);
    text-align: center;
    font-size: 13px;
    color: var(--text-muted);
}

/* ---------- 回到顶部悬浮按钮 ---------- */
.back-to-top {
    position: fixed;
    right: 28px;
    bottom: 32px;
    z-index: 99;
    width: 48px;
    height: 48px;
    border-radius: 50%;
    border: 1px solid rgba(135, 206, 235, 0.3);
    background: rgba(8, 12, 28, 0.72);
    backdrop-filter: blur(16px) saturate(1.4);
    -webkit-backdrop-filter: blur(16px) saturate(1.4);
    color: var(--cyan-400);
    font-size: 18px;
    cursor: pointer;
    display: flex;
    align-items: center;
    justify-content: center;
    opacity: 0;
    transform: translateY(20px) scale(0.9);
    transition: all 0.35s cubic-bezier(0.16, 1, 0.3, 1);
    box-shadow: 0 8px 28px rgba(0, 0, 0, 0.4), 0 0 0 1px rgba(135, 206, 235, 0.08);
    pointer-events: none;
}
.back-to-top.visible {
    opacity: 1;
    transform: translateY(0) scale(1);
    pointer-events: auto;
}
.back-to-top:hover {
    background: rgba(135, 206, 235, 0.22);
    color: #fff;
    transform: translateY(-4px) scale(1.05);
    box-shadow: 0 14px 40px rgba(135, 206, 235, 0.35), 0 0 24px rgba(135, 206, 235, 0.25);
    border-color: rgba(135, 206, 235, 0.6);
}
.back-to-top:active {
    transform: translateY(0) scale(0.95);
}
@media (max-width: 640px) {
    .back-to-top {
        right: 18px;
        bottom: 24px;
        width: 44px;
        height: 44px;
    }
}

/* ---------- 响应式 ---------- */
@media (max-width: 1200px) {
    .hero { grid-template-columns: 1fr; gap: 40px; }
    .hero-visual { height: 450px; }
    .features-grid { grid-template-columns: repeat(2, 1fr); }
    .lang-showcase { grid-template-columns: repeat(2, 1fr); }
    .progress-overview { grid-template-columns: repeat(2, 1fr); }
    .progress-main-grid { grid-template-columns: 1fr; }
    .membership-plans { grid-template-columns: 1fr; max-width: 480px; }
    .community-layout { grid-template-columns: 1fr; }
    .footer-inner { grid-template-columns: 1fr 1fr; }
}
@media (max-width: 1200px) {
    /* 中屏收窄导航间距防溢出，字号保持 16px 不变 */
    .nav-links { gap: 6px; }
    .nav-link { gap: 8px; padding: 10px 14px; }
}
@media (max-width: 1024px) {
    /* 平板及以下：导航收入汉堡菜单，避免挤压换行 */
    .nav-links { display: none; }
    .nav-links.show {
        display: flex;
        position: fixed;
        top: 80px; left: 16px; right: 16px;
        background: rgba(14, 20, 40, 0.98);
        backdrop-filter: blur(20px);
        border: 1px solid var(--border-glass);
        border-radius: var(--radius-lg);
        flex-direction: column;
        padding: 16px;
        gap: 4px;
    }
    .mobile-menu-btn { display: flex; }
}
@media (max-width: 768px) {
    .logo-mark { height: 44px; }
    #app { padding-top: 84px; }
    .hero-title { font-size: 16px; }
    .hero-title .hero-lead { font-size: 34px; letter-spacing: -1px; margin-bottom: 12px; }
    .hero-title .hero-langs { font-size: 24px; letter-spacing: -0.5px; white-space: normal; }
    .hero-stats { flex-wrap: wrap; gap: 24px; }
    .features-grid { grid-template-columns: 1fr; }
    .lang-showcase { grid-template-columns: 1fr; }
    .section { padding: 60px 20px; }
    .progress-overview { grid-template-columns: repeat(2, 1fr); }
    .footer-inner { grid-template-columns: 1fr; gap: 32px; }
}

/* ---------- 工具类 ---------- */
.text-gradient {
    background: var(--gradient-primary);
    -webkit-background-clip: text;
    -webkit-text-fill-color: transparent;
    background-clip: text;
}
.text-center { text-align: center; }
.text-muted { color: var(--text-muted); }
.mt-16 { margin-top: 16px; }
.mt-24 { margin-top: 24px; }
.mt-32 { margin-top: 32px; }
.mb-16 { margin-bottom: 16px; }
.mb-24 { margin-bottom: 24px; }
.flex-center { display: flex; align-items: center; justify-content: center; }
.glass {
    background: var(--bg-card);
    backdrop-filter: blur(20px);
    border: 1px solid var(--border-glass);
}
.empty-state {
    text-align: center;
    padding: 60px 20px;
    color: var(--text-muted);
}
.empty-state i { font-size: 48px; margin-bottom: 16px; opacity: 0.4; }

/* ============ 法律页面（服务条款/隐私政策/退款政策） ============ */
.legal-page {
    max-width: 860px;
    margin: 0 auto;
    padding: 140px 24px 96px;
}
.legal-hero {
    margin-bottom: 40px;
    padding-bottom: 24px;
    border-bottom: 1px solid rgba(255, 255, 255, 0.08);
}
.legal-hero h1 {
    font-family: var(--font-display);
    font-size: 34px;
    font-weight: 700;
    letter-spacing: -0.5px;
    color: var(--text-primary);
    margin-bottom: 10px;
}
.legal-updated {
    font-size: 13px;
    color: var(--text-muted);
}
.legal-section {
    margin-bottom: 32px;
}
.legal-section h3 {
    font-family: var(--font-display);
    font-size: 18px;
    font-weight: 600;
    color: var(--text-primary);
    margin-bottom: 12px;
}
.legal-section p {
    font-size: 14.5px;
    line-height: 1.85;
    color: var(--text-secondary);
    margin-bottom: 10px;
}
@media (max-width: 640px) {
    .legal-page { padding: 110px 18px 72px; }
    .legal-hero h1 { font-size: 26px; }
}

/* ========================================
   课程播放器（课程内页 · 课时课件）
   ======================================== */
.course-player-head {
    display: flex;
    align-items: center;
    gap: 16px;
    margin-bottom: 20px;
    flex-wrap: wrap;
}
.course-player-course {
    font-weight: 600;
    font-size: 15px;
}
.course-player {
    display: grid;
    grid-template-columns: 280px 1fr;
    gap: 24px;
    align-items: start;
}
.lesson-list {
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-lg);
    padding: 12px;
    position: sticky;
    top: 88px;
    max-height: calc(100vh - 120px);
    overflow: auto;
}
.lesson-list-head {
    display: flex;
    justify-content: space-between;
    font-size: 13px;
    color: var(--text-muted);
    padding: 8px 12px;
}
.lesson-progress {
    color: var(--indigo-500);
    font-weight: 600;
}
.lesson-item {
    display: flex;
    align-items: center;
    gap: 10px;
    width: 100%;
    padding: 10px 12px;
    border: none;
    border-radius: var(--radius-md);
    background: transparent;
    color: var(--text-primary);
    font-size: 13px;
    text-align: left;
    cursor: pointer;
    transition: all 0.2s;
}
.lesson-item:hover {
    background: rgba(255, 255, 255, 0.05);
}
.lesson-item.active {
    background: var(--gradient-primary);
    color: #fff;
}
.lesson-item.done .lesson-name {
    opacity: 0.75;
}
.lesson-item i {
    margin-left: auto;
    color: #22c55e;
}
.lesson-item.active i {
    color: #fff;
}
.lesson-icon {
    font-size: 14px;
}
.lesson-body {
    min-height: 420px;
}
.lesson-head {
    display: flex;
    justify-content: space-between;
    align-items: flex-start;
    gap: 16px;
    margin-bottom: 20px;
}
.lesson-eyebrow {
    font-size: 12px;
    color: var(--text-muted);
    margin-bottom: 6px;
}
.lesson-title {
    font-family: var(--font-display);
    font-size: 22px;
}
.lesson-head-actions {
    display: flex;
    gap: 8px;
}
.course-word-grid {
    display: grid;
    grid-template-columns: repeat(auto-fill, minmax(240px, 1fr));
    gap: 16px;
}
.course-word-card {
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-md);
    padding: 18px;
}
.cw-word {
    font-size: 20px;
    font-weight: 700;
}
.cw-phonetic {
    font-size: 12px;
    color: var(--indigo-500);
    margin: 4px 0 8px;
}
.cw-meaning {
    font-size: 14px;
    margin-bottom: 10px;
}
.cw-example {
    font-size: 13px;
    color: var(--text-muted);
}
.cw-example-zh {
    font-size: 12px;
    color: var(--text-muted);
    opacity: 0.8;
    margin-top: 2px;
}
.course-quiz,
.course-speak,
.course-listen {
    background: var(--bg-card);
    border: 1px solid var(--border-glass);
    border-radius: var(--radius-md);
    padding: 18px;
    margin-bottom: 14px;
}
.cq-index {
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 22px;
    height: 22px;
    border-radius: 50%;
    background: var(--gradient-primary);
    color: #fff;
    font-size: 12px;
    font-weight: 700;
    margin-bottom: 8px;
}
.cq-question {
    font-size: 15px;
    font-weight: 600;
    margin-bottom: 12px;
}
.cq-options {
    display: flex;
    flex-direction: column;
    gap: 8px;
    margin-bottom: 12px;
}
.cq-option {
    font-size: 13px;
    padding: 8px 12px;
    border-radius: 8px;
    background: rgba(255, 255, 255, 0.04);
}
.cq-details summary,
.cl-details summary {
    cursor: pointer;
    font-size: 13px;
    color: var(--indigo-500);
}
.cq-answer {
    margin-top: 10px;
    font-size: 13px;
    color: #22c55e;
}
.cq-explain {
    margin-top: 6px;
    font-size: 13px;
    color: var(--text-muted);
}
.cs-text,
.cl-text {
    font-size: 16px;
    font-weight: 600;
    margin-bottom: 8px;
}
.cs-translation,
.cl-translation {
    font-size: 13px;
    color: var(--text-muted);
}
.cs-tip {
    margin-top: 10px;
    font-size: 12px;
    color: var(--indigo-500);
}
.cl-label {
    font-size: 12px;
    color: var(--text-muted);
    margin-bottom: 8px;
}
.cl-details summary {
    margin-top: 8px;
}
.lesson-foot {
    margin-top: 24px;
    display: flex;
    justify-content: flex-end;
}
@media (max-width: 900px) {
    .course-player { grid-template-columns: 1fr; }
    .lesson-list { position: static; max-height: 260px; }
}