/* Base & Theme */
*{box-sizing:border-box}
:root{
	--bg:#0b1220; /* 深色背景 */
	--panel:#0f172a; /* 面板 */
	--card:#0b1220; /* 卡片底 */
	--text:#e5e7eb; /* 文字 */
	--muted:#94a3b8; /* 次要文字 */
	/* 白色半透明主题主色（用于按钮/进度/高亮） */
	--primary:rgba(255,255,255,.92);
	--primary-2:rgba(255,255,255,.78);
	--border:rgba(255,255,255,.12);
	--ring:rgba(255,255,255,.35);
	--shadow:0 10px 25px rgba(2,6,23,.35);
	--danger:#ef4444;
	--success:#10b981;
}
html,body{height:100%}
body{
	margin:0;
	font-family:system-ui,-apple-system,BlinkMacSystemFont,"Segoe UI",Roboto,Ubuntu,"Helvetica Neue",Arial,"Noto Sans","Apple Color Emoji","Segoe UI Emoji";
	color:var(--text);
	background:var(--bg);
	line-height:1.6;
}
a,.bg-canvas{will-change:transform}
.bg-canvas{
	position:fixed;inset:0;z-index:0;pointer-events:none;
	background:
		radial-gradient(1200px 600px at 10% -10%, rgba(255,255,255,.12), transparent 60%),
		radial-gradient(900px 500px at 120% 10%, rgba(255,255,255,.08), transparent 60%),
		linear-gradient(180deg, rgba(255,255,255,.03), rgba(255,255,255,0));
}

/* Scroll progress bar */
#scroll-progress{position:fixed;top:0;left:0;height:3px;width:0;background:linear-gradient(90deg,var(--primary),var(--primary-2));z-index:3;box-shadow:0 2px 8px rgba(255,255,255,.25)}

/* Layout containers */
.container{width:min(1200px,100%);margin:0 auto;padding:0 16px}

/* Sticky header with glassmorphism */
.site-header{position:sticky;top:0;z-index:2;background:rgba(15,23,42,.5);border-bottom:1px solid var(--border);backdrop-filter:blur(10px) saturate(140%)}
.site-header .container{display:flex;align-items:center;justify-content:space-between;padding:10px 20px}

.logo a{font-weight:800;font-size:22px;color:#fff;letter-spacing:.3px}
.nav{display:flex;gap:10px;align-items:center}
.nav a{color:#e2e8f0;padding:8px 10px;border-radius:8px;border:1px solid transparent}
.nav a:hover{background:rgba(148,163,184,.08);border-color:rgba(148,163,184,.2)}
.nav-toggle{display:none;background:transparent;border:1px solid var(--border);color:#e2e8f0;border-radius:8px;padding:8px}

@media (max-width: 768px){
	.nav{display:none;position:absolute;right:16px;top:60px;background:rgba(15,23,42,.98);border:1px solid var(--border);border-radius:12px;box-shadow:var(--shadow);flex-direction:column;padding:8px;width:min(80vw,320px)}
	.nav.open{display:flex}
	.nav-toggle{display:inline-flex}
}

/* Sections & Typography */
h1,h2,h3,h4{margin:0 0 8px}
h2{font-size:28px;letter-spacing:.2px}
a{color:#e5e7eb;text-decoration:none}
p{color:#cbd5e1}
.hero h2{font-size:34px;line-height:1.25;background:linear-gradient(90deg,#fff, rgba(255,255,255,.7));-webkit-background-clip:text;background-clip:text;-webkit-text-fill-color:transparent}
.hero p{font-size:16px;color:var(--muted)}
.hero-banner{padding:32px 0 8px}
.section-eyebrow{color:#a3b2c7;font-size:12px;letter-spacing:.12em;text-transform:uppercase;margin-bottom:6px}

/* Grid & Cards */
.grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:18px}
.features-split{display:grid;gap:18px}
.feature-split-row{display:grid;grid-template-columns:1.2fr 1fr;gap:18px;align-items:center;border:1px solid var(--border);border-radius:14px;background:linear-gradient(180deg, rgba(255,255,255,.06), rgba(255,255,255,.03));backdrop-filter:blur(8px);padding:14px}
.feature-split-row.reverse{grid-template-columns:1fr 1.2fr}
.feature-split-row.reverse .feature-split-media{order:2}
.feature-split-row.reverse .feature-split-content{order:1}
.feature-split-media{position:relative}
.feature-split-media img{
	width:100%;
	height:100%;
	max-height:220px;
	object-fit:cover;
	border-radius:10px;
	aspect-ratio:16/9;
}
.feature-split-placeholder{display:flex;align-items:center;justify-content:center;height:200px;border-radius:10px;background:repeating-linear-gradient(45deg, rgba(255,255,255,.06) 0 12px, rgba(255,255,255,.03) 12px 24px);color:#cbd5e1}
.split-actions{margin-top:8px}
.carousel{display:grid;grid-auto-flow:column;grid-auto-columns:calc(100% - 64px);overflow:auto;gap:14px;scroll-snap-type:x mandatory;padding-bottom:6px}
.carousel::-webkit-scrollbar{height:8px}
.carousel::-webkit-scrollbar-thumb{background:rgba(148,163,184,.25);border-radius:8px}
.carousel-item{scroll-snap-align:start;min-width:320px}
.carousel-nav{display:flex;justify-content:flex-end;gap:8px;margin-top:10px}
.card{
	border:1px solid var(--border);
	border-radius:14px;
	padding:16px;
	background:linear-gradient(180deg, rgba(255,255,255,.08), rgba(255,255,255,.04));
	box-shadow:0 1px 0 rgba(255,255,255,.06) inset, var(--shadow);
	backdrop-filter:blur(10px) saturate(140%);
	transition:transform .18s ease, box-shadow .18s ease, border-color .18s ease, background .18s ease;
}
.card:hover{transform:translateY(-2px);border-color:rgba(255,255,255,.35);box-shadow:0 1px 0 rgba(255,255,255,.06) inset, 0 16px 30px rgba(2,6,23,.5)}
.card img{display:block;width:100%;border-radius:10px;aspect-ratio:16/9;object-fit:cover}

/* Animations */
@keyframes fadeUp{from{opacity:0;transform:translateY(6px)} to{opacity:1;transform:none}}
.hero,.section .grid>.card,.features>.feature-card{animation:fadeUp .35s ease both}

/* Scroll reveal utility */
.reveal{transition:opacity .5s ease, transform .5s ease}
.reveal.reveal-init{opacity:0;transform:translateY(12px)}
.reveal.show{opacity:1;transform:none}

/* Parallax utility */
.parallax{will-change:transform}

/* Accessibility: reduce motion */
@media (prefers-reduced-motion: reduce){
	.reveal,.parallax{transition:none !important;transform:none !important}
	.bg-canvas{filter:none !important;transform:none !important}
}

/* Buttons & Forms */
.btn{display:inline-flex;align-items:center;gap:8px;padding:10px 14px;border-radius:10px;border:1px solid var(--border);background:rgba(148,163,184,.08);color:#e2e8f0;cursor:pointer}
.btn:hover{background:rgba(148,163,184,.12)}
.btn.primary{background:linear-gradient(180deg, var(--primary), var(--primary-2));border-color:transparent;color:#0b1220;box-shadow:0 10px 22px rgba(255,255,255,.18)}
.btn.secondary{background:rgba(148,163,184,.08);border-color:var(--border);color:#e2e8f0}
.btn.danger{background:linear-gradient(180deg, #f43f5e, #ef4444);border-color:transparent;color:#fff;box-shadow:0 10px 22px rgba(239,68,68,.22)}
.btn.small{padding:6px 10px;border-radius:8px}
.btn:focus-visible{outline:none;box-shadow:0 0 0 3px var(--ring)}
.btn-link{padding:6px 10px;border:1px solid var(--border);border-radius:8px;color:#e2e8f0;background:rgba(148,163,184,.06)}
.btn-link:hover{background:rgba(148,163,184,.12)}

.contact-form{display:grid;gap:12px;max-width:540px}
.contact-form input,.contact-form textarea{width:100%;padding:10px 12px;border:1px solid var(--border);border-radius:10px;background:rgba(15,23,42,.6);color:#e2e8f0;outline:0}
.contact-form input:focus,.contact-form textarea:focus{box-shadow:0 0 0 3px var(--ring);border-color:rgba(255,255,255,.4)}
.contact-form button{background:linear-gradient(180deg, var(--primary), var(--primary-2));color:#0b1220;border:none;border-radius:10px;padding:10px 16px;cursor:pointer;box-shadow:0 10px 22px rgba(255,255,255,.18)}
.contact-form input::placeholder,.contact-form textarea::placeholder{color:#93a3b8aa}
.success{padding:10px 12px;background:rgba(16,185,129,.12);border:1px solid rgba(16,185,129,.35);border-radius:10px;color:#d1fae5}

/* Tables */
.table{width:100%;border-collapse:separate;border-spacing:0;overflow:hidden;border:1px solid var(--border);border-radius:14px;background:rgba(148,163,184,.06)}
.table thead th{position:sticky;top:0;background:rgba(15,23,42,.8);backdrop-filter:blur(6px);font-weight:700;color:#e2e8f0}
.table th,.table td{padding:10px 12px;border-bottom:1px solid var(--border);vertical-align:middle}
.table tbody tr:hover{background:rgba(148,163,184,.06)}
.table tbody tr:last-child td{border-bottom:none}
.table img{vertical-align:middle}
.table .btn,.table .btn-link{margin-right:6px}

/* quiz */
.quiz-chapter-list ul{list-style:none;padding:0;margin:0}
.quiz-chapter-list li{padding:10px 0;border-bottom:1px dashed var(--border)}
.muted{color:var(--muted);font-size:12px}
.quiz-form ol{padding-left:20px}
.quiz-item{margin-bottom:14px}
.q-text{font-weight:700;margin-bottom:8px;color:#e2e8f0}
.q-option{display:flex;align-items:flex-start;gap:8px;padding:8px;border:1px solid var(--border);border-radius:10px;margin:6px 0;background:rgba(148,163,184,.04)}
.q-option input{accent-color:var(--primary)}
/* Selected state: make it visibly different before提交 */
.q-option:hover{background:rgba(148,163,184,.08)}
.q-option:has(input:checked){
	/* 深色系（蓝色）选中态，避免与正确答案绿色冲突 */
	background:rgba(59,130,246,.18); /* #3b82f6 */
	border-color:rgba(59,130,246,.45);
}
.q-option:has(input:checked) span{color:#eaf2ff}
.q-option:has(input:focus-visible){box-shadow:0 0 0 3px var(--ring)}
.q-option.right{background:rgba(16,185,129,.12);border-color:rgba(16,185,129,.35)}
.q-option.wrong{background:rgba(239,68,68,.1);border-color:rgba(239,68,68,.35)}
/* 评分后覆盖选中蓝色：对 right/wrong 再次声明，权重更高 */
.q-option.right:has(input:checked){
	background:rgba(16,185,129,.12);
	border-color:rgba(16,185,129,.35);
}
.q-option.wrong:has(input:checked){
	background:rgba(239,68,68,.1);
	border-color:rgba(239,68,68,.35);
}
.q-option.right span{color:#e2e8f0}
.q-option.wrong span{color:#e2e8f0}
.quiz-actions{display:flex;gap:10px;margin-top:12px}
.quiz-actions .secondary{background:rgba(148,163,184,.08);color:#e2e8f0;border:1px solid var(--border)}
.quiz-result{margin-top:12px;padding:12px;border:1px solid var(--border);border-radius:12px;background:rgba(148,163,184,.06)}
.practice-panel{margin-top:14px}
.practice-actions{display:flex;gap:10px;margin-top:10px}

/* Footer */
.site-footer{margin-top:24px;background:transparent;color:var(--muted);border-top:1px solid var(--border);position:relative;z-index:1}
.site-footer .container{display:flex;align-items:center;justify-content:space-between;padding:14px 20px}

/* elevate content above bg-canvas */
main.container{position:relative;z-index:1}

/* Sections */
.section{margin:28px 0}
.hero .actions{display:flex;gap:12px;margin-top:16px;flex-wrap:wrap}

/* Feature cards */
.features{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:16px;margin-top:14px}
.feature-card{border:1px solid var(--border);border-radius:14px;padding:16px;background:linear-gradient(180deg, rgba(255,255,255,.08), rgba(255,255,255,.04));box-shadow:var(--shadow);backdrop-filter:blur(10px) saturate(140%)}
.feature-card:hover{transform:translateY(-2px);border-color:rgba(255,255,255,.3)}
.feature-card h4{margin:0 0 6px;font-size:16px;color:#e2e8f0}
.feature-card p{margin:0;color:var(--muted)}

/* Mosaic variants for homepage feature/testimonial cards */
.features.mosaic .feature-card{position:relative;overflow:hidden}
.features.mosaic .feature-card{perspective:600px;transform-style:preserve-3d}
.features.mosaic .feature-card:hover{transform:translateY(-4px) rotateX(3deg); box-shadow:0 16px 36px rgba(0,0,0,.35)}
.features.mosaic .feature-card:nth-child(1){padding:20px}
.features.mosaic .feature-card:nth-child(1) h4{font-size:18px}
.features.mosaic .feature-card::after{transition:opacity .25s ease}
.features.mosaic .feature-card:hover::after{opacity:.75}
/* 左侧明显的渐变强调条 */
.features.mosaic .feature-card::before{content:"";position:absolute;left:0;top:0;width:4px;height:100%;opacity:.6}
.features.mosaic .feature-card:nth-child(3n+1)::before{background:linear-gradient(180deg,#60a5fa,#a78bfa)}
.features.mosaic .feature-card:nth-child(3n+2)::before{background:linear-gradient(180deg,#34d399,#f59e0b)}
.features.mosaic .feature-card:nth-child(3n+3)::before{background:linear-gradient(180deg,#f472b6,#f43f5e)}
.features.mosaic .feature-card:nth-child(3n+1){
	background:linear-gradient(180deg, rgba(255,255,255,.10), rgba(255,255,255,.05));
	border-color:rgba(96,165,250,.25);
}
.features.mosaic .feature-card:nth-child(3n+1)::before{
	content:"";position:absolute;left:0;right:0;bottom:0;height:3px;
	background:linear-gradient(90deg,#60a5fa,#a78bfa);opacity:.6
}
.features.mosaic .feature-card:nth-child(3n+1)::after{
	content:"";position:absolute;top:-40px;right:-40px;width:140px;height:140px;
	background:radial-gradient(closest-side, rgba(96,165,250,.30), transparent 70%);
	filter:blur(8px)
}
.features.mosaic .feature-card:nth-child(3n+2){
	background:linear-gradient(180deg, rgba(255,255,255,.09), rgba(255,255,255,.045));
	border-color:rgba(34,197,94,.22);
}
.features.mosaic .feature-card:nth-child(3n+2)::before{
	content:"";position:absolute;left:0;top:0;width:100%;height:3px;
	background:linear-gradient(90deg,#34d399,#f59e0b);opacity:.55
}
.features.mosaic .feature-card:nth-child(3n+2)::after{
	content:"";position:absolute;bottom:-48px;left:-48px;width:150px;height:150px;
	background:radial-gradient(closest-side, rgba(52,211,153,.28), transparent 70%);
	filter:blur(10px)
}
.features.mosaic .feature-card:nth-child(3n+3){
	background:
		linear-gradient(180deg, rgba(255,255,255,.085), rgba(255,255,255,.04)),
		repeating-linear-gradient(45deg, rgba(255,255,255,.02) 0 6px, transparent 6px 12px);
	border-color:rgba(236,72,153,.22);
}
.features.mosaic .feature-card:nth-child(3n+3)::before{
	content:"";position:absolute;right:0;top:0;width:6px;height:100%;
	background:linear-gradient(180deg,#f472b6,#f43f5e);opacity:.45
}
.features.mosaic .feature-card:nth-child(3n+3)::after{
	content:"";position:absolute;top:-36px;left:-36px;width:120px;height:120px;
	background:radial-gradient(closest-side, rgba(236,72,153,.26), transparent 70%);
	filter:blur(8px)
}

/* Details (summary) */
details{border:1px solid var(--border);border-radius:12px;padding:10px 12px;background:rgba(148,163,184,.06)}
details[open]{background:rgba(148,163,184,.08)}
details>summary{cursor:pointer;list-style:none;color:#e2e8f0;font-weight:600}
details>summary::-webkit-details-marker{display:none}
details>summary::after{content:'▾';float:right;color:var(--muted)}
details[open]>summary::after{content:'▴'}

/* Images */
img{max-width:100%;height:auto}
/* News thumbnail sizing */
.news-item img{width:160px;max-width:32vw;height:auto;aspect-ratio:16/10;object-fit:cover}

/* News list */
.news-list{list-style:none;padding:0;margin:10px 0;display:grid;grid-template-columns:1fr;gap:10px}
.news-item{border:1px solid var(--border);border-radius:12px;padding:12px;background:rgba(148,163,184,.06);transition:background .2s ease, transform .2s ease, border-color .2s ease}
.news-item:nth-child(even){background:rgba(148,163,184,.08);border-color:rgba(255,255,255,.12)}
.news-item:hover{transform:translateX(2px)}
.news-item small{color:var(--muted)}

/* Home courses card accents */
.home-courses .card{position:relative;overflow:hidden}
.home-courses .card:nth-child(3n+1){border-color:rgba(96,165,250,.22)}
.home-courses .card:nth-child(3n+1)::before{content:"";position:absolute;left:0;top:0;width:100%;height:2px;background:linear-gradient(90deg,#60a5fa,transparent)}
.home-courses .card:nth-child(3n+2){border-color:rgba(34,197,94,.20)}
.home-courses .card:nth-child(3n+2)::before{content:"";position:absolute;left:0;top:0;width:100%;height:2px;background:linear-gradient(90deg,#34d399,transparent)}
.home-courses .card:nth-child(3n+3){border-color:rgba(236,72,153,.20)}
.home-courses .card:nth-child(3n+3)::before{content:"";position:absolute;left:0;top:0;width:100%;height:2px;background:linear-gradient(90deg,#f472b6,transparent)}

/* Home courses: spotlight + sheen + depth */
.home-courses .card{position:relative;overflow:hidden}
.home-courses .card{
	--spot: .10; /* 默认较弱，悬停时提升 */
	background:
		linear-gradient(180deg, rgba(255,255,255,.08), rgba(255,255,255,.04)),
		radial-gradient(300px 220px at var(--mx, 50%) var(--my, 0%), rgba(255,255,255,var(--spot)), transparent 60%);
}
.home-courses .card{transform:translateZ(0);transition:transform .25s ease, box-shadow .25s ease}
.home-courses .card:hover{transform:translateY(-3px) scale(1.01);box-shadow:0 18px 40px rgba(0,0,0,.35)}
.home-courses .card::before{ /* 掠光 */
	content:"";position:absolute;inset:-20%;pointer-events:none;border-radius:14px;
	background:linear-gradient(120deg, transparent 40%, rgba(255,255,255,.15) 50%, transparent 60%);
	transform:translateX(-60%);
	transition:transform .6s ease;
}
.home-courses .card:hover::before{transform:translateX(0%)}
.home-courses .card::after{
	content:"";position:absolute;inset:-2px;pointer-events:none;border-radius:14px;
	background:conic-gradient(from 180deg at 50% 50%, rgba(255,255,255,.08), rgba(255,255,255,0) 20%, rgba(255,255,255,.08) 40%, rgba(255,255,255,0) 60%, rgba(255,255,255,.08) 80%, rgba(255,255,255,0));
	mask:linear-gradient(#000,#000) content-box, linear-gradient(#000,#000);
	-webkit-mask:linear-gradient(#000,#000) content-box, linear-gradient(#000,#000);
	-webkit-mask-composite:xor; mask-composite:exclude; padding:1px; opacity:.35
}
.home-courses .card:hover::after{opacity:.55}
.home-courses .card img,.home-courses .card .video-wrap{border-radius:10px}
.home-courses .card .video-wrap{aspect-ratio:16/9}
.home-courses .card img{transition:transform .25s ease}
.home-courses .card:hover img{transform:scale(1.02)}

/* News alternation */
.news-item{transition:background .2s ease, transform .2s ease, border-color .2s ease}
.news-item:nth-child(even){background:rgba(148,163,184,.08) !important;border-color:rgba(255,255,255,.12) !important}
.news-item:hover{transform:translateX(2px)}