/* ==========================================================================
   YQY Acoustic — single stylesheet
   移动优先 / 零外部依赖 / 低带宽友好（无 web font、无框架）
   改色板只改下面 :root 里的变量
   ========================================================================== */

:root {
  --brand: #0e7c6b;
  --brand-dark: #0a5a4e;
  --brand-soft: #e8f3f1;
  --wood: #b8874a;
  --ink: #10201d;
  --ink-2: #23332f;
  --text: #3b4a46;
  --muted: #6b7a76;
  --line: #e2e9e7;
  --bg: #ffffff;
  --bg-soft: #f5f8f7;
  --bg-dark: #0d1f1b;
  --radius: 10px;
  --radius-lg: 16px;
  --wrap: 1200px;
  --shadow: 0 1px 2px rgba(16,32,29,.06), 0 8px 24px rgba(16,32,29,.06);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0; font-family: var(--font); color: var(--text);
  background: var(--bg); line-height: 1.65; font-size: 16px;
  -webkit-font-smoothing: antialiased;
}
img { max-width: 100%; height: auto; display: block; }
a { color: var(--brand); text-decoration: none; }
a:hover { color: var(--brand-dark); }
h1, h2, h3, h4 { color: var(--ink); line-height: 1.25; margin: 0 0 .6em; font-weight: 700; letter-spacing: -.01em; }
h1 { font-size: 1.75rem; }
h2 { font-size: 1.4rem; }
h3 { font-size: 1.12rem; }
h4 { font-size: 1rem; }
p { margin: 0 0 1em; }
ul, ol { margin: 0 0 1em; padding-left: 1.2em; }
li { margin-bottom: .35em; }
hr { border: 0; border-top: 1px solid var(--line); margin: 2rem 0; }

.wrap { width: 100%; max-width: var(--wrap); margin: 0 auto; padding: 0 18px; }
.wrap-narrow { max-width: 820px; }
.sr-only { position: absolute; width: 1px; height: 1px; overflow: hidden; clip: rect(0 0 0 0); }

/* ---------- buttons ---------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 8px;
  padding: 13px 22px; border-radius: 8px; font-weight: 600; font-size: .95rem;
  border: 1px solid transparent; cursor: pointer; transition: .18s ease;
  text-align: center; line-height: 1.2;
}
.btn-primary { background: var(--brand); color: #fff; }
.btn-primary:hover { background: var(--brand-dark); color: #fff; }
.btn-wa { background: #25d366; color: #08301c; }
.btn-wa:hover { background: #1fbe5b; color: #08301c; }
.btn-ghost { background: transparent; color: var(--ink); border-color: var(--line); }
.btn-ghost:hover { border-color: var(--brand); color: var(--brand); }
.btn-light { background: #fff; color: var(--brand-dark); }
.btn-light:hover { color: var(--brand); }
.btn-block { width: 100%; }
.btn-sm { padding: 9px 15px; font-size: .85rem; }

/* ---------- topbar / header ---------- */
.topbar {
  background: var(--bg-dark); color: #cfe0db; font-size: .8rem;
}
.topbar .wrap { display: flex; flex-wrap: wrap; gap: 6px 18px; align-items: center;
  justify-content: center; padding-top: 7px; padding-bottom: 7px; }
.topbar a { color: #eaf5f2; }
.topbar span.dot { opacity: .35; }

.header { position: sticky; top: 0; z-index: 60; background: #fff; border-bottom: 1px solid var(--line); }
.header .wrap { display: flex; align-items: center; gap: 14px; height: 64px; }
.brand { display: flex; align-items: center; gap: 10px; flex: 0 0 auto; }
.brand img { height: 34px; width: auto; }
.brand-text { font-weight: 800; color: var(--ink); font-size: 1rem; letter-spacing: -.02em; line-height: 1.1; }
.brand-text small { display: block; font-weight: 500; font-size: .62rem; color: var(--muted); letter-spacing: .06em; text-transform: uppercase; }

.nav { margin-left: auto; display: none; }
.nav ul { display: flex; align-items: center; gap: 2px; list-style: none; margin: 0; padding: 0; }
.nav li { position: relative; margin: 0; }
.nav a {
  display: block; padding: 9px 11px; border-radius: 6px; color: var(--ink-2);
  font-size: .87rem; font-weight: 500; white-space: nowrap;
}
.nav a:hover, .nav a[aria-current="page"] { background: var(--brand-soft); color: var(--brand-dark); }
.nav .has-sub > a::after { content: ""; display: inline-block; margin-left: 5px; width: 5px; height: 5px;
  border-right: 1.5px solid currentColor; border-bottom: 1.5px solid currentColor;
  transform: rotate(45deg) translateY(-2px); }
.nav .sub { display: none; position: absolute; top: 100%; left: 0; min-width: 236px;
  background: #fff; border: 1px solid var(--line); border-radius: 10px; box-shadow: var(--shadow);
  padding: 6px; list-style: none; margin: 0; }
.nav .has-sub:hover .sub, .nav .has-sub:focus-within .sub { display: block; }
.nav .sub a { padding: 9px 12px; font-size: .86rem; }

.header-actions { display: flex; align-items: center; gap: 8px; margin-left: auto; }
.header-actions .nav { margin: 0; }
.lang { font-size: .78rem; font-weight: 700; color: var(--muted); padding: 6px 8px;
  border: 1px solid var(--line); border-radius: 6px; }
.lang a { color: var(--muted); }
.lang a:hover { color: var(--brand); }

.burger { display: inline-flex; flex-direction: column; justify-content: center; gap: 5px;
  width: 42px; height: 42px; padding: 0 10px; background: #fff; border: 1px solid var(--line);
  border-radius: 8px; cursor: pointer; }
.burger span { display: block; height: 2px; background: var(--ink); border-radius: 2px; transition: .2s; }

.mobile-nav { display: none; border-top: 1px solid var(--line); background: #fff; }
.mobile-nav.open { display: block; }
.mobile-nav ul { list-style: none; margin: 0; padding: 8px 0; }
.mobile-nav > ul > li { margin: 0; }
.mobile-nav a { display: block; padding: 12px 18px; color: var(--ink-2); font-weight: 500;
  border-bottom: 1px solid #f1f5f4; }
.mobile-nav .sub a { padding-left: 34px; font-weight: 400; font-size: .9rem; color: var(--text); }
.mobile-nav .m-cta { padding: 14px 18px 18px; display: grid; gap: 10px; }

@media (min-width: 1000px) {
  .nav { display: block; }
  .burger { display: none; }
  .mobile-nav { display: none !important; }
  .header .wrap { height: 74px; }
  .brand img { height: 40px; }
  h1 { font-size: 2.6rem; }
  h2 { font-size: 1.85rem; }
  h3 { font-size: 1.25rem; }
}

/* ---------- hero ---------- */
.hero { position: relative; background: var(--bg-dark); color: #eaf5f2; overflow: hidden; }
.hero img.hero-bg { position: absolute; inset: 0; width: 100%; height: 100%; object-fit: cover; opacity: .42; }
.hero::after { content: ""; position: absolute; inset: 0;
  background: linear-gradient(180deg, rgba(8,26,22,.55) 0%, rgba(8,26,22,.82) 100%); }
.hero .wrap { position: relative; z-index: 2; padding-top: 56px; padding-bottom: 56px; }
.hero h1 { color: #fff; font-size: 1.8rem; max-width: 22em; }
.hero p.lead { font-size: 1rem; color: #d3e5e0; max-width: 40em; }
.hero .kicker { display: inline-block; font-size: .72rem; letter-spacing: .14em; text-transform: uppercase;
  color: #9fd9cc; font-weight: 700; margin-bottom: 14px; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 22px; }
.hero-facts { display: grid; grid-template-columns: repeat(2, 1fr); gap: 14px 18px;
  margin-top: 34px; padding-top: 24px; border-top: 1px solid rgba(255,255,255,.16); }
.hero-facts div { font-size: .82rem; color: #b8d3cd; }
.hero-facts strong { display: block; font-size: 1.32rem; color: #fff; font-weight: 800; letter-spacing: -.02em; }
@media (min-width: 768px) {
  .hero .wrap { padding-top: 92px; padding-bottom: 92px; }
  .hero h1 { font-size: 2.9rem; }
  .hero p.lead { font-size: 1.12rem; }
  .hero-facts { grid-template-columns: repeat(4, 1fr); }
}

/* ---------- sections ---------- */
.section { padding: 52px 0; }
.section-soft { background: var(--bg-soft); }
.section-dark { background: var(--bg-dark); color: #cfe0db; }
.section-dark h2, .section-dark h3 { color: #fff; }
.section-dark a { color: #9fd9cc; }
.section-tight { padding: 36px 0; }
@media (min-width: 768px) { .section { padding: 76px 0; } }

.sec-head { max-width: 760px; margin-bottom: 32px; }
.sec-head.center { margin-left: auto; margin-right: auto; text-align: center; }
.eyebrow { display: block; font-size: .72rem; letter-spacing: .16em; text-transform: uppercase;
  color: var(--brand); font-weight: 700; margin-bottom: 10px; }
.sec-head p { color: var(--muted); font-size: .98rem; margin: 0; }

/* ---------- grids / cards ---------- */
.grid { display: grid; gap: 18px; }
.grid-2, .grid-3, .grid-4 { grid-template-columns: 1fr; }
@media (min-width: 620px) {
  .grid-2 { grid-template-columns: repeat(2, 1fr); }
  .grid-4 { grid-template-columns: repeat(2, 1fr); }
}
@media (min-width: 860px) {
  .grid-3 { grid-template-columns: repeat(3, 1fr); }
  .grid-4 { grid-template-columns: repeat(4, 1fr); }
  .grid-6 { grid-template-columns: repeat(6, 1fr); }
}

.card { background: #fff; border: 1px solid var(--line); border-radius: var(--radius-lg);
  overflow: hidden; transition: .2s ease; display: flex; flex-direction: column; }
.card:hover { border-color: #cfe0db; box-shadow: var(--shadow); transform: translateY(-2px); }
.card-img { position: relative; background: #eef3f2; overflow: hidden; }
.card-img img { width: 100%; height: 100%; object-fit: cover; transition: .4s ease; }
.card:hover .card-img img { transform: scale(1.03); }
.card-body { padding: 16px 18px 20px; flex: 1; display: flex; flex-direction: column; }
.card-body h3 { margin-bottom: 6px; font-size: 1.05rem; }
.card-body p { color: var(--muted); font-size: .9rem; margin: 0 0 14px; }
.card-body .more { margin-top: auto; font-weight: 600; font-size: .88rem; }
.card .badge { position: absolute; top: 10px; left: 10px; background: rgba(13,31,27,.82);
  color: #fff; font-size: .7rem; font-weight: 700; letter-spacing: .06em; padding: 5px 9px; border-radius: 5px; }

.ratio-1x1 { aspect-ratio: 1/1; }
.ratio-4x3 { aspect-ratio: 4/3; }
.ratio-3x2 { aspect-ratio: 3/2; }
.ratio-16x9 { aspect-ratio: 16/9; }
.ratio-3x4 { aspect-ratio: 3/4; }
.ratio-2x1 { aspect-ratio: 2/1; }
.ratio-4x5 { aspect-ratio: 4/5; }
.ratio-5x4 { aspect-ratio: 5/4; }
.ratio-9x16 { aspect-ratio: 9/16; }
.ratio-10x16 { aspect-ratio: 10/16; }
.ratio-1x2 { aspect-ratio: 1/2; }
.ratio-2x3 { aspect-ratio: 2/3; }
img[class*="ratio-"] { width: 100%; object-fit: cover; border-radius: var(--radius); }

/* feature / value tiles */
.tile { background: #fff; border: 1px solid var(--line); border-radius: var(--radius); padding: 20px; }
.tile .ico { width: 38px; height: 38px; margin-bottom: 12px; color: var(--brand); }
.tile h3 { font-size: 1rem; margin-bottom: 6px; }
.tile p { font-size: .88rem; color: var(--muted); margin: 0; }

/* split block */
.split { display: grid; gap: 26px; align-items: center; }
.split.flip .split-media { order: -1; }
.split-media img { border-radius: var(--radius-lg); width: 100%; }
@media (min-width: 860px) {
  .split { grid-template-columns: 1fr 1fr; gap: 48px; }
  .split.flip .split-media { order: 2; }
}

/* ---------- spec table ---------- */
.spec-table { width: 100%; border-collapse: collapse; font-size: .9rem; }
.spec-table th, .spec-table td { text-align: left; padding: 11px 12px; border-bottom: 1px solid var(--line); vertical-align: top; }
.spec-table th { width: 40%; color: var(--ink); font-weight: 600; background: #fafcfb; }
.spec-table tr:last-child td, .spec-table tr:last-child th { border-bottom: 0; }
.table-wrap { border: 1px solid var(--line); border-radius: var(--radius); overflow-x: auto; background: #fff; }

/* ---------- product detail ---------- */
.crumb { font-size: .8rem; color: var(--muted); padding: 14px 0; }
.crumb a { color: var(--muted); }
.crumb a:hover { color: var(--brand); }
.crumb span { margin: 0 6px; opacity: .5; }

.pd-top { display: grid; gap: 24px; }
@media (min-width: 900px) { .pd-top { grid-template-columns: 1.15fr .85fr; gap: 40px; align-items: start; } }
.pd-main { border: 1px solid var(--line); border-radius: var(--radius-lg); overflow: hidden; background: #eef3f2; }
.pd-thumbs { display: grid; grid-template-columns: repeat(5, 1fr); gap: 8px; margin-top: 10px; }
.pd-thumbs button { padding: 0; border: 2px solid transparent; border-radius: 7px; overflow: hidden;
  background: #eef3f2; cursor: pointer; }
.pd-thumbs button.active { border-color: var(--brand); }
.pd-thumbs img { aspect-ratio: 1/1; object-fit: cover; width: 100%; }
.pd-side h1 { font-size: 1.5rem; }
.pd-side .code { display: inline-block; font-size: .74rem; font-weight: 700; letter-spacing: .1em;
  background: var(--brand-soft); color: var(--brand-dark); padding: 4px 9px; border-radius: 5px; margin-bottom: 12px; }
.pd-price-note { background: var(--bg-soft); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 14px 16px; font-size: .85rem; margin: 18px 0; }
.pd-price-note strong { display: block; color: var(--ink); margin-bottom: 4px; }
.pd-actions { display: grid; gap: 10px; margin: 18px 0; }
.pd-facts { list-style: none; padding: 0; margin: 18px 0 0; border-top: 1px solid var(--line); }
.pd-facts li { display: flex; justify-content: space-between; gap: 16px; padding: 10px 0;
  border-bottom: 1px solid var(--line); font-size: .88rem; margin: 0; }
.pd-facts li b { color: var(--ink); font-weight: 600; }

/* thickness selector */
.thumbs-row { display: grid; grid-template-columns: repeat(2, 1fr); gap: 10px; margin: 20px 0; }
@media (min-width: 620px) { .thumbs-row { grid-template-columns: repeat(5, 1fr); } }
.thick-opt { border: 1px solid var(--line); border-radius: 9px; padding: 12px 10px; background: #fff;
  text-align: center; cursor: pointer; transition: .16s; font: inherit; color: var(--text); }
.thick-opt b { display: block; font-size: 1.05rem; color: var(--ink); }
.thick-opt small { font-size: .72rem; color: var(--muted); }
.thick-opt[aria-pressed="true"] { border-color: var(--brand); background: var(--brand-soft); box-shadow: inset 0 0 0 1px var(--brand); }

/* filters */
.filters { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 24px; }
.filters button { font: inherit; font-size: .86rem; font-weight: 600; padding: 9px 16px; border-radius: 999px;
  border: 1px solid var(--line); background: #fff; color: var(--ink-2); cursor: pointer; }
.filters button[aria-pressed="true"] { background: var(--brand); border-color: var(--brand); color: #fff; }
.filter-count { font-size: .82rem; color: var(--muted); margin-bottom: 14px; }

/* CTA band */
.cta-band { background: linear-gradient(135deg, var(--brand-dark), #0d5a4d 60%, #146e5e); color: #eaf5f2; }
.cta-band .wrap { padding: 46px 18px; }
.cta-band h2 { color: #fff; }
.cta-band p { color: #c8e2dc; max-width: 46em; }
.cta-band .hero-actions { margin-top: 18px; }

/* ---------- forms ---------- */
.form { display: grid; gap: 14px; }
.field { display: grid; gap: 6px; }
.field label { font-size: .84rem; font-weight: 600; color: var(--ink); }
.field .req { color: #c0392b; }
.field input, .field select, .field textarea {
  font: inherit; font-size: .92rem; padding: 11px 13px; border: 1px solid #d7e0de;
  border-radius: 8px; background: #fff; color: var(--text); width: 100%;
}
.field input:focus, .field select:focus, .field textarea:focus {
  outline: none; border-color: var(--brand); box-shadow: 0 0 0 3px rgba(14,124,107,.12);
}
.field textarea { min-height: 110px; resize: vertical; }
.form-row { display: grid; gap: 14px; }
@media (min-width: 640px) { .form-row { grid-template-columns: 1fr 1fr; } }
.form-note { font-size: .8rem; color: var(--muted); margin: 0; }
.form-status { font-size: .86rem; padding: 11px 14px; border-radius: 8px; display: none; }
.form-status.show { display: block; }
.form-status.ok { background: var(--brand-soft); color: var(--brand-dark); }
.form-status.err { background: #fdeceb; color: #a4322a; }

/* ---------- accordion ---------- */
.acc { border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; background: #fff; }
.acc details { border-bottom: 1px solid var(--line); }
.acc details:last-child { border-bottom: 0; }
.acc summary { cursor: pointer; padding: 16px 18px; font-weight: 600; color: var(--ink);
  font-size: .95rem; list-style: none; display: flex; justify-content: space-between; gap: 14px; }
.acc summary::-webkit-details-marker { display: none; }
.acc summary::after { content: "+"; color: var(--brand); font-size: 1.2rem; line-height: 1; font-weight: 400; }
.acc details[open] summary::after { content: "–"; }
.acc .acc-body { padding: 0 18px 16px; font-size: .9rem; color: var(--text); }
.acc .acc-body p:last-child { margin-bottom: 0; }

/* ---------- misc ---------- */
.pills { display: flex; flex-wrap: wrap; gap: 8px; list-style: none; padding: 0; margin: 0 0 18px; }
.pills li { margin: 0; font-size: .8rem; padding: 6px 12px; border-radius: 999px;
  background: var(--brand-soft); color: var(--brand-dark); font-weight: 600; }
.note { font-size: .82rem; color: var(--muted); background: var(--bg-soft);
  border-left: 3px solid var(--brand); padding: 12px 14px; border-radius: 0 8px 8px 0; }
.tag { display: inline-block; font-size: .72rem; font-weight: 700; letter-spacing: .08em;
  text-transform: uppercase; color: var(--wood); }
.link-more { font-weight: 600; font-size: .9rem; }
.wa-float { position: fixed; right: 16px; bottom: 16px; z-index: 80; display: inline-flex;
  align-items: center; gap: 9px; background: #25d366; color: #08301c; font-weight: 700;
  font-size: .88rem; padding: 13px 17px; border-radius: 999px;
  box-shadow: 0 8px 22px rgba(11,60,40,.28); }
.wa-float:hover { color: #08301c; background: #1fbe5b; }
.wa-float svg { width: 20px; height: 20px; }
@media (max-width: 520px) { .wa-float span.t { display: none; } .wa-float { padding: 14px; } }

/* footer */
.footer { background: var(--bg-dark); color: #a9c2bc; padding: 52px 0 0; font-size: .89rem; }
.footer h4 { color: #fff; font-size: .8rem; letter-spacing: .12em; text-transform: uppercase; margin-bottom: 14px; }
.footer a { color: #cfe0db; }
.footer a:hover { color: #fff; }
.footer .f-top { display: grid; gap: 32px; padding-bottom: 36px; }
@media (min-width: 760px) { .footer .f-top { grid-template-columns: 1.6fr 1fr 1fr 1.2fr; gap: 40px; } }
.footer .f-brand img { height: 36px; width: auto; margin-bottom: 14px; }
.footer ul { list-style: none; padding: 0; margin: 0; }
.footer ul li { margin-bottom: 8px; }
.footer .f-bottom { border-top: 1px solid rgba(255,255,255,.1); padding: 18px 0;
  display: flex; flex-wrap: wrap; gap: 8px 20px; justify-content: space-between; font-size: .8rem; color: #7f9a94; }

/* print / reduced motion */
@media (prefers-reduced-motion: reduce) { * { transition: none !important; animation: none !important; } }