:root{
  --red:#c0392b;
  --black:#0b0b0c;
  --ink:#111113;
  --gray-900:#1d1d1f;
  --gray-600:#6e6e73;
  --gray-300:#d2d2d7;
  --gray-100:#f5f5f7;
  --white:#ffffff;
  --font: -apple-system, BlinkMacSystemFont, "SF Pro Display", "PingFang SC", "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  --ease: cubic-bezier(.16,1,.3,1);
}

*{box-sizing:border-box; margin:0; padding:0;}
html{scroll-behavior:smooth;}
body{
  font-family:var(--font);
  color:var(--ink);
  background:var(--white);
  -webkit-font-smoothing:antialiased;
  overflow-x:hidden;
}
img{max-width:100%; display:block;}
a{color:inherit; text-decoration:none;}
section{position:relative;}

.eyebrow{
  font-size:14px; font-weight:600; letter-spacing:.04em;
  text-transform:uppercase; color:var(--red); margin-bottom:12px;
}
h1,h2,h3{font-weight:700; letter-spacing:-0.02em; line-height:1.05;}
h2{font-size:clamp(28px,4vw,44px); color:var(--gray-900);}
h3{font-size:22px; color:var(--gray-900); margin-bottom:10px;}
p{color:var(--gray-600); line-height:1.6; font-size:17px;}

.btn{
  display:inline-block; padding:14px 28px; border-radius:980px;
  font-size:16px; font-weight:600; cursor:pointer; border:1px solid transparent;
  transition:transform .25s var(--ease), background .25s var(--ease), color .25s var(--ease);
}
.btn:hover{transform:translateY(-2px);}
.btn-primary{background:var(--red); color:var(--white);}
.btn-primary:hover{background:#a5301f;}
.btn-ghost{background:rgba(255,255,255,.08); color:var(--white); border-color:rgba(255,255,255,.4); backdrop-filter:blur(6px);}
.btn-ghost:hover{background:rgba(255,255,255,.18);}
.vip .btn-primary, .practice .btn-primary{color:var(--white);}

/* ---------- NAV ---------- */
.nav{
  position:fixed; top:0; left:0; right:0; z-index:100;
  background:rgba(11,11,12,.55); backdrop-filter:blur(14px) saturate(150%);
  border-bottom:1px solid rgba(255,255,255,.08);
  transition:background .3s var(--ease);
}
.nav-inner{
  max-width:1120px; margin:0 auto; padding:14px 24px;
  display:flex; align-items:center; justify-content:space-between;
}
.nav-logo{display:flex; align-items:center; gap:10px; color:var(--white); font-weight:600; font-size:15px;}
.nav-logo img{width:28px; height:28px; border-radius:50%; object-fit:cover;}
.nav-logo em{color:var(--red); font-style:normal;}
.nav-links{display:flex; gap:28px;}
.nav-links a{color:rgba(255,255,255,.85); font-size:14px; transition:color .2s;}
.nav-links a:hover{color:var(--white);}
.nav-cta{
  background:var(--red); color:var(--white); font-size:13px; font-weight:600;
  padding:8px 18px; border-radius:980px; transition:background .2s;
}
.nav-cta:hover{background:#a5301f;}

/* ---------- HERO ---------- */
.hero{
  min-height:100svh; position:relative; overflow:hidden;
  display:flex; align-items:center; justify-content:center;
  background:radial-gradient(120% 100% at 15% 15%, #26100c 0%, var(--black) 55%);
  padding:140px 24px 80px;
}
.hero-inner{
  max-width:1120px; width:100%; margin:0 auto;
  display:grid; grid-template-columns:1.1fr .9fr; gap:56px; align-items:center;
}
.hero-content{color:var(--white); text-align:left;}
.hero .eyebrow{color:#ff8a75;}
.hero h1{
  font-size:clamp(40px,5.5vw,72px); margin-bottom:18px; color:var(--white);
}
.hero h1 .hl{color:var(--red);}
.hero-sub{
  color:rgba(255,255,255,.85); font-size:clamp(16px,2vw,19px);
  max-width:480px; margin:0 0 34px;
}
.hero-actions{display:flex; gap:16px; flex-wrap:wrap;}

.hero-media{
  position:relative; display:block; width:auto; height:min(68svh, 620px); margin:0 auto;
  aspect-ratio:9/16; border-radius:32px; overflow:hidden; cursor:pointer;
  box-shadow:0 40px 80px -30px rgba(0,0,0,.6); border:1px solid rgba(255,255,255,.08);
  transition:transform .3s var(--ease), box-shadow .3s var(--ease);
}
.hero-media:hover{transform:translateY(-4px); box-shadow:0 48px 90px -28px rgba(0,0,0,.7);}
.hero-media video{width:100%; height:100%; object-fit:cover; display:block;}
.hero-media-badge{
  position:absolute; left:50%; bottom:18px; transform:translateX(-50%);
  background:rgba(0,0,0,.55); backdrop-filter:blur(6px); color:var(--white);
  font-size:13px; font-weight:600; padding:8px 16px; border-radius:980px;
  white-space:nowrap; opacity:0; transition:opacity .25s var(--ease);
}
.hero-media:hover .hero-media-badge{opacity:1;}

.scroll-cue{
  position:absolute; bottom:28px; left:50%; transform:translateX(-50%); z-index:2;
  width:24px; height:38px; border:2px solid rgba(255,255,255,.5); border-radius:14px;
}
.scroll-cue span{
  display:block; width:4px; height:8px; background:var(--white); border-radius:2px;
  margin:6px auto 0; animation:scrollcue 1.8s infinite var(--ease);
}
@keyframes scrollcue{
  0%{transform:translateY(0); opacity:1;}
  70%{transform:translateY(12px); opacity:0;}
  100%{opacity:0;}
}

/* ---------- SECTION SHELL ---------- */
.section-head{max-width:680px; margin:0 auto 56px; text-align:center; padding:0 24px;}
.section-sub{margin-top:14px;}

.teachers, .why, .practice, .vip{padding:120px 24px;}
.teachers{background:var(--white);}
.why{background:var(--gray-100);}
.practice{background:var(--white);}
.vip{background:var(--black);}

/* ---------- TEACHERS ---------- */
.teacher-cards{
  max-width:1000px; margin:0 auto; display:grid;
  grid-template-columns:repeat(2,1fr); gap:32px;
}
.teacher-card{
  background:var(--gray-900); border-radius:28px; padding:40px 32px; text-align:center;
  color:var(--white);
}
.teacher-photo{
  width:180px; height:180px; margin:0 auto 24px; border-radius:50%;
  overflow:hidden; background:#e9e9ec; display:flex; align-items:flex-end; justify-content:center;
}
.teacher-photo img{width:100%; height:100%; object-fit:cover; object-position:top center;}
.teacher-card h3{color:var(--white);}
.teacher-role{color:var(--red); font-weight:600; font-size:14px; text-transform:uppercase; letter-spacing:.03em; margin-bottom:14px;}
.teacher-bio{color:rgba(255,255,255,.72);}

/* ---------- WHY / FEATURES ---------- */
.feature-row{
  max-width:1000px; margin:0 auto 90px; display:grid;
  grid-template-columns:1.1fr .9fr; gap:56px; align-items:center;
}
.feature-row:last-child{margin-bottom:0;}
.feature-row.reverse{grid-template-columns:.9fr 1.1fr;}
.feature-row.reverse .feature-text{order:2;}
.feature-row.reverse .feature-visual{order:1;}
.feature-visual{
  display:flex; flex-direction:column; gap:14px;
}
.word-chip{
  background:var(--white); border:1px solid var(--gray-300); border-radius:18px;
  padding:20px 26px; font-size:28px; font-weight:700; color:var(--gray-900);
  display:flex; align-items:baseline; justify-content:space-between; gap:16px;
  box-shadow:0 12px 30px -18px rgba(0,0,0,.25);
}
.word-chip span{font-size:14px; font-weight:500; color:var(--gray-600); white-space:nowrap;}

/* ---------- PRACTICE GAME ---------- */
.game{max-width:560px; margin:0 auto;}
.game-top{display:flex; justify-content:center; gap:48px; margin-bottom:32px;}
.game-stat{text-align:center;}
.game-stat span{display:block; font-size:32px; font-weight:700; color:var(--red);}
.game-stat label{font-size:13px; color:var(--gray-600); text-transform:uppercase; letter-spacing:.03em;}

.game-card{
  background:var(--gray-100); border-radius:28px; padding:48px 32px; text-align:center;
}
.game-hanzi{font-size:64px; font-weight:700; color:var(--gray-900); margin-bottom:6px;}
/* 音标含 ʊ ː ŋ ɜ 等 IPA 字符，指定系统里一定有这些字形的字体 */
.game-sound, .sound{font-family:"Segoe UI","Lucida Sans Unicode","Arial Unicode MS",sans-serif;}
.game-sound{font-size:20px; color:var(--gray-600); margin-bottom:24px; min-height:28px;}
.game-input-row{display:flex; gap:12px;}
.game-input{
  flex:1; padding:14px 18px; border-radius:980px; border:1px solid var(--gray-300);
  font-size:17px; font-family:var(--font); outline:none; transition:border-color .2s;
}
.game-input:focus{border-color:var(--red);}
.game-feedback{margin-top:16px; font-weight:600; font-size:15px; min-height:20px;}
.game-feedback.ok{color:#1e8e3e;}
.game-feedback.no{color:var(--red);}
.game-hint{text-align:center; margin-top:20px; font-size:14px;}
.game-hint code{background:var(--gray-100); padding:2px 6px; border-radius:6px; font-size:13px;}

/* ---------- VIP ---------- */
.vip-card{max-width:640px; margin:0 auto; text-align:center; color:var(--white);}
.vip-card h2{color:var(--white);}
.vip-sub{color:rgba(255,255,255,.7); margin:16px auto 32px; max-width:520px;}
.vip-form{display:flex; gap:12px; max-width:420px; margin:0 auto; flex-wrap:wrap; justify-content:center;}
.vip-form input{
  flex:1; min-width:220px; padding:14px 20px; border-radius:980px; border:1px solid rgba(255,255,255,.25);
  background:rgba(255,255,255,.08); color:var(--white); font-size:16px; outline:none; font-family:var(--font);
}
.vip-form input::placeholder{color:rgba(255,255,255,.45);}
.vip-form input:focus{border-color:var(--red);}
.vip-note{margin-top:16px; font-size:14px; color:rgba(255,255,255,.7);}

/* ---------- FOOTER ---------- */
.footer{
  padding:40px 24px; text-align:center; background:var(--black); color:rgba(255,255,255,.5);
  display:flex; flex-direction:column; align-items:center; gap:12px; font-size:13px;
}
.footer img{width:32px; height:32px; border-radius:50%; object-fit:cover;}

/* ---------- REVEAL ANIMATION ---------- */
.reveal{opacity:0; transform:translateY(28px); transition:opacity .8s var(--ease), transform .8s var(--ease);}
.reveal.in-view{opacity:1; transform:translateY(0);}
.teacher-cards .teacher-card:nth-child(2){transition-delay:.12s;}

/* ---------- RESPONSIVE ---------- */
@media (max-width:820px){
  .nav-links{display:none;}
  .hero{padding:120px 20px 60px;}
  .hero-inner{grid-template-columns:1fr; text-align:center; gap:40px;}
  .hero-content{text-align:center;}
  .hero-sub{margin-left:auto; margin-right:auto;}
  .hero-actions{justify-content:center;}
  .hero-media{height:min(50svh, 420px);}
  .teacher-cards{grid-template-columns:1fr;}
  .feature-row, .feature-row.reverse{grid-template-columns:1fr; gap:28px;}
  .feature-row.reverse .feature-text, .feature-row.reverse .feature-visual{order:initial;}
  .teachers, .why, .practice, .vip{padding:88px 20px;}
  .game-input-row{flex-direction:column;}
  .game-input-row .btn{width:100%;}
}