/* 溯言 SureSay — 落地页样式
   视觉与 App 一致：白底 + 发丝线 + 近黑 + emerald(#059669)
   亮/暗随系统（prefers-color-scheme），无 JS */
:root {
  --accent: #059669;
  --accent-strong: #047857;
  --accent-soft: rgba(5, 150, 105, .1);
  --bg: #ffffff;
  --bg-soft: #f7f8f7;
  --card: #ffffff;
  --line: rgba(17, 24, 22, .08);
  --line-strong: rgba(17, 24, 22, .14);
  --text: #10201b;
  --text-2: #5b6963;
  --text-3: #93a09a;
  --ink: #10201b;            /* 近黑实心钮底色 */
  --ink-text: #ffffff;
  --shadow: 0 20px 60px rgba(16, 32, 27, .1);
  --radius: 20px;
  --max: 1120px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --accent: #10B981;
    --accent-strong: #34D399;
    --accent-soft: rgba(16, 185, 129, .14);
    --bg: #0d1512;
    --bg-soft: #111b17;
    --card: #16211c;
    --line: rgba(255, 255, 255, .08);
    --line-strong: rgba(255, 255, 255, .14);
    --text: #edf5f1;
    --text-2: #9fb0a8;
    --text-3: #66756e;
    --ink: #edf5f1;
    --ink-text: #0d1512;
    --shadow: 0 20px 60px rgba(0, 0, 0, .45);
  }
}

* { margin: 0; padding: 0; box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  font-family: -apple-system, "PingFang SC", "Microsoft YaHei", "Segoe UI", Roboto, sans-serif;
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
a { color: inherit; text-decoration: none; }
img { display: block; }
.wrap { max-width: var(--max); margin: 0 auto; padding: 0 24px; }

/* ---------- 顶栏 ---------- */
header.nav {
  position: sticky; top: 0; z-index: 20;
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  background: color-mix(in srgb, var(--bg) 78%, transparent);
  border-bottom: 1px solid var(--line);
}
.nav .wrap { display: flex; align-items: center; justify-content: space-between; height: 64px; gap: 18px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 800; font-size: 18px; letter-spacing: .2px; }
.brand .logo { width: 32px; height: 32px; border-radius: 9px; }
.brand small { color: var(--text-3); font-weight: 600; font-size: 12.5px; letter-spacing: .8px; }
.nav-links { display: flex; gap: 26px; color: var(--text-2); font-size: 15px; }
.nav-links a:hover { color: var(--text); }
.nav .btn { padding: 9px 20px; font-size: 14.5px; }

/* ---------- 按钮 ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  background: var(--ink); color: var(--ink-text);
  font-weight: 700; font-size: 16px;
  padding: 13px 28px; border-radius: 999px; border: none; cursor: pointer;
  transition: transform .15s ease, opacity .15s ease;
}
.btn:hover { transform: translateY(-2px); opacity: .92; }
.btn.ghost {
  background: transparent; color: var(--text);
  border: 1px solid var(--line-strong);
}
.btn.accent { background: var(--accent); color: #fff; }

/* ---------- Hero ---------- */
.hero { position: relative; overflow: hidden; border-bottom: 1px solid var(--line); }
.hero::before {
  content: ""; position: absolute; inset: -40% -20% auto;
  height: 130%;
  background:
    radial-gradient(560px 420px at 18% 8%, var(--accent-soft), transparent 68%),
    radial-gradient(640px 460px at 86% 22%, var(--accent-soft), transparent 70%);
  pointer-events: none;
}
.hero .wrap {
  position: relative;
  display: grid; grid-template-columns: 1.08fr .92fr; gap: 48px;
  align-items: center; padding-top: 76px; padding-bottom: 84px;
}
.eyebrow {
  display: inline-flex; align-items: center; gap: 8px;
  color: var(--accent); font-weight: 700; font-size: 13.5px; letter-spacing: 1.5px;
  border: 1px solid color-mix(in srgb, var(--accent) 30%, transparent);
  background: var(--accent-soft);
  padding: 6px 14px; border-radius: 999px;
}
.hero h1 { font-size: 56px; line-height: 1.1; font-weight: 800; letter-spacing: -1.5px; margin-top: 22px; }
.hero h1 .grad { color: var(--accent); }
.hero p.sub { color: var(--text-2); font-size: 19px; margin-top: 20px; max-width: 520px; }
.hero .cta { margin-top: 34px; display: flex; gap: 14px; flex-wrap: wrap; }
.hero .note { margin-top: 18px; color: var(--text-3); font-size: 13px; }

/* Hero 右侧手机模型 */
.phone {
  width: 320px; margin-left: auto;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 42px; padding: 14px;
  box-shadow: var(--shadow);
}
.phone .screen {
  background: var(--bg-soft); border-radius: 30px; padding: 18px 14px 22px;
  display: flex; flex-direction: column; gap: 12px; min-height: 480px;
}
.phone .p-top { display: flex; align-items: center; gap: 9px; padding: 2px 4px 8px; border-bottom: 1px solid var(--line); }
.phone .p-ava {
  width: 30px; height: 30px; border-radius: 50%;
  background: linear-gradient(135deg, #10B981, #047857);
  display: grid; place-items: center; color: #fff; font-size: 14px; font-weight: 800;
}
.phone .p-name { font-size: 13.5px; font-weight: 700; }
.phone .p-name small { display: block; color: var(--accent); font-weight: 600; font-size: 10.5px; }
.bubble {
  max-width: 84%; padding: 10px 14px; border-radius: 16px;
  font-size: 13px; line-height: 1.5;
}
.bubble.ai { background: var(--card); border: 1px solid var(--line); border-top-left-radius: 6px; align-self: flex-start; }
.bubble.ai small { display: block; color: var(--text-3); font-size: 11px; margin-top: 3px; }
.bubble.me { background: var(--accent); color: #fff; border-top-right-radius: 6px; align-self: flex-end; }
/* 跟读课句卡（Hero 手机模型） */
.lesson-sent {
  background: var(--card); border: 1px solid var(--line);
  border-radius: 16px; padding: 14px;
}
.lesson-sent .en { font-size: 14px; font-weight: 700; line-height: 1.5; }
.lesson-sent .en i { font-style: normal; color: var(--accent); border-bottom: 2px solid var(--accent); }
.lesson-sent .zh { font-size: 11.5px; color: var(--text-3); margin-top: 6px; }
.sent-ops { display: flex; gap: 8px; margin-top: 10px; }
.sent-ops span {
  font-size: 10.5px; color: var(--text-2);
  border: 1px solid var(--line); border-radius: 999px; padding: 3px 10px;
}
.sent-next { padding: 2px 6px; }
.sent-next .en.dim { font-size: 12.5px; color: var(--text-3); font-weight: 500; }
.scorecard {
  align-self: flex-end; max-width: 84%;
  background: var(--card); border: 1px solid var(--line); border-radius: 14px;
  padding: 10px 14px; font-size: 11.5px; color: var(--text-2);
}
.scorecard .s-row { display: flex; align-items: center; gap: 8px; margin-top: 6px; }
.scorecard .s-num { font-size: 20px; font-weight: 800; color: var(--accent); line-height: 1; }
.scorecard .s-bar { flex: 1; height: 5px; border-radius: 999px; background: var(--line); overflow: hidden; }
.scorecard .s-bar i { display: block; height: 100%; border-radius: 999px; background: var(--accent); }
.wavebtn {
  margin-top: auto; align-self: center;
  width: 56px; height: 56px; border-radius: 50%;
  background: var(--ink); display: grid; place-items: center;
}
.wavebtn .bars { display: flex; align-items: center; gap: 4px; height: 22px; }
.wavebtn .bars i { width: 4px; border-radius: 99px; background: var(--ink-text); animation: eq 1.1s ease-in-out infinite; }
.wavebtn .bars i:nth-child(1) { height: 10px; animation-delay: 0s; }
.wavebtn .bars i:nth-child(2) { height: 20px; animation-delay: .18s; }
.wavebtn .bars i:nth-child(3) { height: 14px; animation-delay: .36s; }
@keyframes eq { 0%,100% { transform: scaleY(.55); } 50% { transform: scaleY(1); } }
@media (prefers-reduced-motion: reduce) { .wavebtn .bars i { animation: none; } }

/* ---------- 区块通用 ---------- */
section { padding: 84px 0; }
section.alt { background: var(--bg-soft); border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); }
.section-head { text-align: center; margin-bottom: 52px; }
.section-head h2 { font-size: 36px; font-weight: 800; letter-spacing: -.5px; }
.section-head p { color: var(--text-2); margin-top: 12px; font-size: 17px; }

/* ---------- 双 App 卡 ---------- */
.apps { display: grid; grid-template-columns: 1fr 1fr; gap: 24px; }
.app-card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: calc(var(--radius) + 6px); padding: 36px;
  display: flex; flex-direction: column;
  transition: transform .18s ease, box-shadow .18s ease;
}
.app-card:hover { transform: translateY(-4px); box-shadow: var(--shadow); }
.app-head { display: flex; align-items: center; gap: 16px; }
.app-head img { width: 64px; height: 64px; border-radius: 15px; }
.app-head h3 { font-size: 23px; font-weight: 800; letter-spacing: -.3px; }
.app-head .tag {
  display: inline-block; margin-top: 4px;
  color: var(--accent); font-size: 12.5px; font-weight: 700; letter-spacing: .5px;
}
.app-card > p { color: var(--text-2); font-size: 15.5px; margin-top: 18px; }
.app-feats { list-style: none; margin: 22px 0 28px; display: grid; gap: 11px; }
.app-feats li { display: flex; gap: 10px; font-size: 14.5px; color: var(--text-2); }
.app-feats li::before {
  content: "✓"; flex: none;
  width: 20px; height: 20px; border-radius: 50%;
  background: var(--accent-soft); color: var(--accent);
  display: grid; place-items: center; font-size: 11px; font-weight: 800;
  margin-top: 2px;
}
.app-feats li b { color: var(--text); font-weight: 700; white-space: nowrap; }
.app-card .cta { margin-top: auto; display: flex; gap: 10px; flex-wrap: wrap; }
.app-card .btn { padding: 11px 22px; font-size: 14.5px; }

/* ---------- 数字带 ---------- */
.stats { display: grid; grid-template-columns: repeat(4, 1fr); gap: 18px; }
.stat { text-align: center; padding: 26px 10px; border-radius: var(--radius); border: 1px solid var(--line); background: var(--card); }
.stat b { display: block; font-size: 32px; font-weight: 800; letter-spacing: -1px; color: var(--accent); }
.stat span { color: var(--text-2); font-size: 13.5px; }

/* ---------- 能力网格 ---------- */
.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.card {
  background: var(--card); border: 1px solid var(--line);
  border-radius: var(--radius); padding: 28px;
}
.card .ico {
  width: 46px; height: 46px; border-radius: 13px;
  background: var(--accent-soft);
  display: grid; place-items: center; font-size: 22px; margin-bottom: 16px;
}
.card h3 { font-size: 18.5px; font-weight: 700; }
.card p { color: var(--text-2); margin-top: 8px; font-size: 14.5px; }

/* ---------- 步骤 ---------- */
.steps { display: grid; grid-template-columns: repeat(3, 1fr); gap: 20px; }
.step { text-align: center; padding: 10px; }
.step .num {
  width: 46px; height: 46px; border-radius: 50%; margin: 0 auto 14px;
  display: grid; place-items: center; font-weight: 800; font-size: 17px;
  background: var(--ink); color: var(--ink-text);
}
.step h3 { font-size: 18px; }
.step p { color: var(--text-2); font-size: 14.5px; margin-top: 6px; }

/* ---------- CTA 带 ---------- */
.cta-band {
  background: var(--ink); color: var(--ink-text);
  border-radius: 32px; padding: 64px 40px; text-align: center;
}
.cta-band h2 { font-size: 34px; font-weight: 800; letter-spacing: -.5px; }
.cta-band p { opacity: .72; margin: 14px 0 30px; font-size: 17px; }
.cta-band .btn { background: var(--accent); color: #fff; }
.cta-band .btn.ghost { background: transparent; color: var(--ink-text); border: 1px solid color-mix(in srgb, var(--ink-text) 28%, transparent); }
.cta-band .note { margin-top: 18px; font-size: 13px; opacity: .5; }

/* ---------- 页脚 ---------- */
footer { border-top: 1px solid var(--line); padding: 44px 0; color: var(--text-3); font-size: 14px; }
footer .wrap { display: flex; justify-content: space-between; flex-wrap: wrap; gap: 20px; }
footer a { color: var(--text-2); }
footer a:hover { color: var(--text); }
.footer-links { display: flex; gap: 22px; flex-wrap: wrap; }

/* ---------- 法律页 ---------- */
.legal { padding: 60px 0; max-width: 800px; }
.legal h1 { font-size: 32px; margin-bottom: 8px; letter-spacing: -.5px; }
.legal .updated { color: var(--text-3); margin-bottom: 32px; }
.legal h2 { font-size: 20px; margin: 28px 0 10px; }
.legal p, .legal li { color: var(--text-2); margin: 8px 0; }
.legal ul { padding-left: 22px; }
.legal a { color: var(--accent); }

/* ---------- 响应式 ---------- */
@media (max-width: 900px) {
  .hero .wrap { grid-template-columns: 1fr; padding-top: 56px; padding-bottom: 56px; text-align: center; }
  .hero p.sub { margin-left: auto; margin-right: auto; }
  .hero .cta { justify-content: center; }
  .phone { margin: 8px auto 0; }
  .apps { grid-template-columns: 1fr; }
  .stats { grid-template-columns: repeat(2, 1fr); }
}
@media (max-width: 760px) {
  .hero h1 { font-size: 38px; }
  .section-head h2 { font-size: 28px; }
  .grid, .steps { grid-template-columns: 1fr; }
  .nav-links { display: none; }
  .cta-band { padding: 44px 22px; }
}