/* Tunelight / 弦光 — dark stage, one accent (in-tune green). */
:root {
  --stage: #0A0A0C;
  --raised: #141417;
  --line: #222226;
  --ink: #F5F5F7;
  --ink2: #A1A1A6;
  --accent: #4EE3A3;
  color-scheme: dark;
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--stage);
  color: var(--ink);
  font: 17px/1.6 -apple-system, BlinkMacSystemFont, "SF Pro Text", "SF Pro", "Segoe UI", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--ink); text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { color: var(--accent); }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 4px; }
.wrap { width: min(1080px, 100% - 48px); margin-inline: auto; }

/* ---------- Hero ---------- */
.hero { padding: 72px 0 0; position: relative; overflow: hidden; }
.hero::before { /* the spotlight, as on the app's stage */
  content: ""; position: absolute; inset: -30% 10% auto; height: 120%;
  background: radial-gradient(closest-side, rgba(255,255,255,.07), transparent 70%);
  pointer-events: none;
}
.hero-grid { position: relative; display: grid; gap: 48px; align-items: center; grid-template-columns: 1fr; }
.hero-grid.has-shot { grid-template-columns: 1.15fr .85fr; }
.app-id { display: flex; align-items: center; gap: 14px; margin-bottom: 28px; }
.app-id img { width: 64px; height: 64px; border-radius: 15px; box-shadow: 0 0 0 1px rgba(255,255,255,.08); }
.app-id span { font-size: 22px; font-weight: 650; letter-spacing: -.01em; }
h1 {
  margin: 0; max-width: 17ch;
  font-size: clamp(2.5rem, 6.4vw, 4.25rem); line-height: 1.04;
  font-weight: 700; letter-spacing: -.035em;
}
:lang(zh) h1 { letter-spacing: -.01em; line-height: 1.15; max-width: 12em; }
.sub { margin: 22px 0 0; max-width: 34em; color: var(--ink2); font-size: clamp(1.06rem, 1.6vw, 1.2rem); }
.shot { margin: 0; justify-self: center; width: min(320px, 72vw); }
.shot img { display: block; width: 100%; height: auto; border-radius: 44px; box-shadow: 0 0 0 1px rgba(255,255,255,.1), 0 30px 80px rgba(0,0,0,.6); }

/* Signature: six strings; a green light sweeps across once, like the app's "all in tune" moment. */
.strings { position: relative; margin-top: 64px; height: 84px; display: flex; flex-direction: column; justify-content: space-between; }
.strings i {
  display: block; height: 1px; background: var(--line); position: relative; overflow: hidden;
}
.strings i:nth-child(1) { height: 3px; } .strings i:nth-child(2) { height: 2.5px; } .strings i:nth-child(3) { height: 2px; }
.strings i:nth-child(4) { height: 1.5px; } .strings i:nth-child(5) { height: 1px; } .strings i:nth-child(6) { height: 1px; }
.strings i::after {
  content: ""; position: absolute; inset: 0; background: var(--accent);
  box-shadow: 0 0 12px var(--accent);
  transform-origin: left; transform: scaleX(0); opacity: .9;
  animation: sweep 1.6s cubic-bezier(.3,.7,.2,1) forwards;
}
.strings i:nth-child(2)::after { animation-delay: .06s; } .strings i:nth-child(3)::after { animation-delay: .12s; }
.strings i:nth-child(4)::after { animation-delay: .18s; } .strings i:nth-child(5)::after { animation-delay: .24s; }
.strings i:nth-child(6)::after { animation-delay: .3s; }
@keyframes sweep { 0% { transform: scaleX(0); } 100% { transform: scaleX(1); opacity: .55; } }

/* ---------- Highlights ---------- */
.highlights { display: grid; grid-template-columns: repeat(2, 1fr); gap: 1px; background: var(--line); border: 1px solid var(--line); border-radius: 20px; overflow: hidden; margin: 56px 0 0; }
.highlights div { background: var(--stage); padding: 28px 28px 30px; }
.highlights h2 { margin: 0 0 8px; font-size: 1.25rem; line-height: 1.3; font-weight: 650; letter-spacing: -.01em; }
.highlights p { margin: 0; color: var(--ink2); }

/* ---------- Download ---------- */
.download { margin: 56px 0 0; display: flex; flex-wrap: wrap; align-items: baseline; gap: 8px 20px; }
.download strong { font-size: 1.25rem; font-weight: 650; }
.download span { color: var(--ink2); }
.download { align-items: center; }
.download .badge { display: inline-block; padding: 13px 13px 13px 0; line-height: 0; }
.download .badge img { display: block; height: 50px; width: auto; }

/* ---------- Docs pages (support, privacy) ---------- */
.doc { padding: 56px 0 0; }
.doc .app-id { margin-bottom: 36px; }
.doc .app-id a { display: flex; align-items: center; gap: 14px; text-decoration: none; }
.doc h1 { font-size: clamp(2.25rem, 5vw, 3.25rem); max-width: none; }
.doc .lede { margin: 16px 0 0; color: var(--ink2); max-width: 40em; font-size: 1.12rem; }
.doc section { max-width: 44em; margin-top: 44px; }
.doc h2 { margin: 0 0 10px; font-size: 1.25rem; font-weight: 650; letter-spacing: -.01em; }
.doc p, .doc li { color: var(--ink2); }
.doc p { margin: 0 0 12px; }
.doc ul { margin: 0; padding-left: 1.2em; }
.doc li { margin: 4px 0; }
.doc strong { color: var(--ink); font-weight: 600; }
.contact { margin-top: 36px; max-width: 44em; padding: 26px 28px; border: 1px solid var(--line); border-radius: 20px; background: var(--raised); }
.contact h2 { margin: 0 0 8px; font-size: 1.25rem; font-weight: 650; }
.contact p { margin: 0; color: var(--ink2); }
.contact .mail { display: inline-block; margin: 6px 0 10px; font-size: 1.35rem; font-weight: 650; color: var(--accent); word-break: break-all; }
.faq { max-width: 44em; margin-top: 48px; }
.faq h2.section { font-size: 1.5rem; margin: 0 0 8px; letter-spacing: -.015em; }
.faq details { border-bottom: 1px solid var(--line); }
.faq summary { cursor: pointer; list-style: none; padding: 18px 32px 18px 0; position: relative; font-weight: 600; color: var(--ink); }
.faq summary::-webkit-details-marker { display: none; }
.faq summary::after { content: "+"; position: absolute; right: 4px; top: 15px; font-size: 1.3rem; font-weight: 400; color: var(--ink2); }
.faq details[open] summary::after { content: "–"; }
.faq details p { margin: 0 0 18px; color: var(--ink2); }
.meta { color: var(--ink2); font-size: .95rem; }

/* ---------- Footer ---------- */
footer { margin-top: 88px; padding: 28px 0 40px; border-top: 1px solid var(--line); color: var(--ink2); font-size: .94rem; }
footer .wrap { display: flex; flex-wrap: wrap; gap: 10px 24px; align-items: center; }
footer a { color: var(--ink2); text-decoration: none; }
footer a:hover, footer a[aria-current="page"] { color: var(--ink); }
footer .lang { margin-left: auto; }

@media (max-width: 820px) {
  .hero { padding-top: 48px; }
  .hero-grid.has-shot { grid-template-columns: 1fr; }
  .highlights { grid-template-columns: 1fr; }
  .strings { margin-top: 48px; height: 64px; }
  footer .lang { margin-left: 0; }
}
@media (max-width: 400px) {
  .wrap { width: calc(100% - 36px); }
  .highlights div { padding: 22px 20px 24px; }
  .contact { padding: 22px 20px; }
}
@media (prefers-reduced-motion: reduce) {
  .strings i::after { animation: none; transform: scaleX(1); opacity: .55; }
}