/* ==========================================================================
   ZH Tech — premium stylesheet (v2: richer, tighter)
   Clean and refined, but with more substance and closer spacing.
   ========================================================================== */

:root {
  --ink: #1d1d1f;
  --ink-2: #58585c;
  --ink-3: #86868b;
  --line: #e3e3e6;
  --line-soft: #eeeef0;
  --bg: #ffffff;
  --bg-alt: #f5f5f7;
  --accent: #0066cc;
  --accent-press: #004e9e;
  --accent-tint: rgba(0,102,204,0.10);
  --dark: #1d1d1f;
  --radius: 24px;
  --radius-btn: 980px;
  --focus: #0a84ff;
  --maxw: 1080px;
  --measure: 660px;
}

* { box-sizing: border-box; }

html { font-size: 18px; -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation: none !important; transition: none !important; }
}

body {
  margin: 0;
  font-family: -apple-system, BlinkMacSystemFont, "SF Pro Display", "SF Pro Text",
    "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  line-height: 1.5;
  color: var(--ink);
  background: var(--bg);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

.wrap { width: 100%; max-width: var(--maxw); margin-inline: auto; padding-inline: 24px; }
.narrow { max-width: var(--measure); margin-inline: auto; }
.center { text-align: center; }

section { padding-block: clamp(58px, 8vw, 104px); }
.band { background: var(--bg-alt); }
.band-dark { background: var(--dark); color: #fff; }

/* Type -------------------------------------------------------------------- */
h1, h2, h3 { margin: 0; font-weight: 650; letter-spacing: -0.021em; overflow-wrap: break-word; }
h1 { font-size: clamp(2.2rem, 8.4vw, 4.3rem); line-height: 1.06; }
h2 { font-size: clamp(1.8rem, 5.2vw, 2.9rem); line-height: 1.1; }
h3 { font-size: clamp(1.25rem, 3.6vw, 1.55rem); line-height: 1.2; letter-spacing: -0.015em; }

.eyebrow { font-size: 0.95rem; font-weight: 600; color: var(--accent); margin: 0 0 12px; letter-spacing: 0.002em; }
.eyebrow.muted { color: var(--ink-3); }

p { margin: 0; }
.sub { font-size: clamp(1.1rem, 1.8vw, 1.35rem); line-height: 1.45; color: var(--ink-2); font-weight: 400; }
.body { font-size: 1.06rem; color: var(--ink-2); line-height: 1.55; }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* Skip + focus ------------------------------------------------------------ */
.skip { position: absolute; left: -9999px; top: 0; background: var(--ink); color: #fff; padding: 14px 20px; border-radius: 0 0 12px 0; z-index: 100; }
.skip:focus { left: 0; }
a:focus-visible, button:focus-visible, .btn:focus-visible, summary:focus-visible { outline: 3px solid var(--focus); outline-offset: 3px; border-radius: 8px; }

/* Buttons ----------------------------------------------------------------- */
.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: 10px;
  min-height: 52px; padding: 12px 28px;
  font-size: 1.08rem; font-weight: 500;
  text-decoration: none; border-radius: var(--radius-btn);
  border: 1.5px solid transparent; cursor: pointer;
  transition: transform 0.14s ease, background 0.2s ease, border-color 0.2s ease;
}
.btn:hover { text-decoration: none; }
.btn:active { transform: scale(0.98); }
.btn svg { width: 21px; height: 21px; flex: 0 0 auto; }
.btn-primary { background: var(--accent); color: #fff; }
.btn-primary:hover { background: var(--accent-press); }
.btn-secondary { background: rgba(0,0,0,0.055); color: var(--ink); }
.btn-secondary:hover { background: rgba(0,0,0,0.10); }
.btn-lg { min-height: 56px; font-size: 1.14rem; padding: 14px 34px; }
.band-dark .btn-primary { background: var(--accent); color: #fff; }
.band-dark .btn-primary:hover { background: #1a7fe0; }
.band-dark .btn-secondary { background: rgba(255,255,255,0.14); color: #fff; }
.band-dark .btn-secondary:hover { background: rgba(255,255,255,0.22); }

/* Header ------------------------------------------------------------------ */
.site-header {
  position: sticky; top: 0; z-index: 40;
  background: rgba(255,255,255,0.72);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-bottom: 1px solid rgba(0,0,0,0.06);
}
.header-row { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 64px; }
.brand { display: inline-flex; align-items: center; gap: 12px; text-decoration: none; color: var(--ink); }
.brand:hover { text-decoration: none; }
.brand .mono { width: 38px; height: 38px; border-radius: 10px; background: var(--ink); color: #fff; display: grid; place-items: center; font-weight: 600; font-size: 0.95rem; }
.brand .name { font-weight: 600; font-size: 1.14rem; letter-spacing: -0.01em; }
.brand .name small { display: block; font-weight: 400; font-size: 0.7rem; color: var(--ink-3); margin-top: 1px; }
.header-cta { min-height: 40px; padding: 8px 20px; font-size: 0.98rem; display: none; }
@media (min-width: 720px) { .header-cta { display: inline-flex; } }

/* Hero -------------------------------------------------------------------- */
.hero { position: relative; padding-block: clamp(56px, 9vw, 100px); text-align: center; overflow: hidden; }
.hero::before { content: ""; position: absolute; inset: -20% 0 auto 0; height: 560px; background: radial-gradient(720px 400px at 50% 0%, rgba(0,102,204,0.10), rgba(0,102,204,0) 62%); pointer-events: none; }
.hero > .wrap { position: relative; }
.hero h1 { margin-bottom: 20px; }
.hero .sub { max-width: 620px; margin-inline: auto; }
.hero-actions { display: flex; flex-wrap: wrap; gap: 13px; justify-content: center; margin-top: 30px; }
.hero .callnote { margin-top: 18px; font-size: 0.98rem; color: var(--ink-3); }

.reveal { opacity: 1; }
@media (prefers-reduced-motion: no-preference) {
  .reveal { opacity: 0; animation: fadeUp 0.8s cubic-bezier(0.2,0.7,0.2,1) forwards; }
  .d1 { animation-delay: 0.06s; } .d2 { animation-delay: 0.13s; } .d3 { animation-delay: 0.2s; } .d4 { animation-delay: 0.27s; }
}
@keyframes fadeUp { from { opacity: 0; transform: translateY(14px); } to { opacity: 1; transform: none; } }

/* Trust strip ------------------------------------------------------------- */
.trust { border-top: 1px solid var(--line); border-bottom: 1px solid var(--line); background: var(--bg); }
.trust .wrap { padding-block: 26px; }
.trust-grid { display: grid; grid-template-columns: repeat(2, 1fr); gap: 20px 26px; }
@media (min-width: 780px) { .trust-grid { grid-template-columns: repeat(4, 1fr); } }
.trust-item { display: flex; align-items: center; gap: 12px; }
.trust-item .ic { flex: 0 0 auto; width: 38px; height: 38px; border-radius: 11px; background: var(--accent-tint); color: var(--accent); display: grid; place-items: center; }
.trust-item .ic svg { width: 20px; height: 20px; }
.trust-item span { font-size: 1.0rem; font-weight: 500; color: var(--ink); line-height: 1.25; }

/* Section head ------------------------------------------------------------ */
.head { text-align: center; max-width: 720px; margin: 0 auto clamp(34px, 5vw, 56px); }
.head .sub { margin-top: 14px; }

/* Feature tiles ----------------------------------------------------------- */
.tiles { display: grid; gap: 24px; grid-template-columns: 1fr; }
@media (min-width: 880px) { .tiles { grid-template-columns: 1fr 1fr; } }
.tile { background: var(--bg); border: 1px solid var(--line); border-radius: var(--radius); padding: clamp(28px, 3.4vw, 44px); }
.band .tile { background: #fff; box-shadow: 0 1px 3px rgba(0,0,0,0.04); }
.tile-icon { width: 50px; height: 50px; border-radius: 14px; background: var(--accent-tint); color: var(--accent); display: grid; place-items: center; margin-bottom: 20px; }
.tile-icon svg { width: 26px; height: 26px; }
.tile h3 { margin-bottom: 8px; }
.tile > .body { margin-bottom: 4px; }

.feat { list-style: none; padding: 0; margin: 18px 0 0; }
.feat li { display: flex; align-items: flex-start; gap: 12px; padding: 9px 0; font-size: 1.04rem; color: var(--ink); border-top: 1px solid var(--line-soft); }
.feat li:first-child { border-top: 0; padding-top: 4px; }
.chk { flex: 0 0 auto; width: 21px; height: 21px; margin-top: 2px; border-radius: 50%; background: var(--accent-tint); color: var(--accent); display: grid; place-items: center; }
.chk svg { width: 12px; height: 12px; }
.tile .note { margin-top: 18px; font-size: 0.96rem; color: var(--ink-3); line-height: 1.5; }

.work { display: flex; flex-wrap: wrap; gap: 9px; margin-top: 16px; }
.work a { display: inline-flex; align-items: center; gap: 7px; background: rgba(0,0,0,0.045); border-radius: 980px; padding: 8px 16px; font-size: 0.94rem; font-weight: 500; color: var(--ink); text-decoration: none; transition: background 0.2s ease; }
.work a:hover { background: rgba(0,0,0,0.09); text-decoration: none; }

/* Steps ------------------------------------------------------------------- */
.steps { display: grid; gap: 34px; grid-template-columns: 1fr; max-width: 920px; margin: 0 auto; }
@media (min-width: 760px) { .steps { grid-template-columns: repeat(3, 1fr); gap: 30px; } }
.step { text-align: center; }
.step .num { font-size: 2.9rem; font-weight: 600; color: var(--accent); opacity: 0.28; letter-spacing: -0.02em; line-height: 1; margin-bottom: 10px; }
.step h3 { font-size: 1.3rem; margin-bottom: 6px; }
.step p { color: var(--ink-2); font-size: 1.02rem; }

/* FAQ --------------------------------------------------------------------- */
.faq { max-width: 780px; margin: 0 auto; }
.faq details { border-top: 1px solid var(--line); }
.faq details:last-child { border-bottom: 1px solid var(--line); }
.faq summary {
  list-style: none; cursor: pointer;
  display: flex; align-items: center; justify-content: space-between; gap: 18px;
  padding: 22px 4px; font-size: 1.16rem; font-weight: 600; color: var(--ink);
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary .pm { flex: 0 0 auto; width: 26px; height: 26px; position: relative; color: var(--accent); transition: transform 0.2s ease; }
.faq summary .pm::before, .faq summary .pm::after { content: ""; position: absolute; background: currentColor; border-radius: 2px; }
.faq summary .pm::before { top: 12px; left: 4px; width: 18px; height: 2.5px; }
.faq summary .pm::after { top: 4px; left: 12px; width: 2.5px; height: 18px; transition: transform 0.2s ease; }
.faq details[open] summary .pm::after { transform: rotate(90deg); }
.faq .ans { padding: 0 4px 24px; color: var(--ink-2); font-size: 1.06rem; line-height: 1.6; max-width: 680px; }

/* Contact (dark, tightened) ----------------------------------------------- */
.band-dark { padding-block: clamp(52px, 7vw, 88px); }
.band-dark .eyebrow { color: #6aa9ff; }
.band-dark h2 { color: #fff; }
.band-dark .sub { color: #a1a1a6; margin-top: 12px; }
.contact-actions { display: flex; flex-wrap: wrap; gap: 13px; justify-content: center; margin-top: 26px; }
.band-dark .callnote { margin-top: 18px; font-size: 0.98rem; color: #86868b; }
.band-dark .callnote a { color: #6aa9ff; }

/* Footer ------------------------------------------------------------------ */
.site-footer { padding-block: 28px; border-top: 1px solid var(--line); color: var(--ink-3); font-size: 0.9rem; }
.footer-row { display: flex; flex-wrap: wrap; gap: 8px 24px; align-items: center; justify-content: space-between; }
.site-footer a { color: var(--ink-3); }
.site-footer a:hover { color: var(--ink); }

/* Sticky mobile bar ------------------------------------------------------- */
.callbar {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 50;
  display: flex; gap: 10px; padding: 10px 14px calc(10px + env(safe-area-inset-bottom));
  background: rgba(255,255,255,0.82);
  backdrop-filter: saturate(180%) blur(20px); -webkit-backdrop-filter: saturate(180%) blur(20px);
  border-top: 1px solid rgba(0,0,0,0.08);
}
.callbar .btn { flex: 1; min-height: 50px; font-size: 1.06rem; }
body { padding-bottom: 78px; }
@media (min-width: 720px) { .callbar { display: none; } body { padding-bottom: 0; } }

/* Dark mode --------------------------------------------------------------- */
@media (prefers-color-scheme: dark) {
  :root {
    --ink: #f5f5f7; --ink-2: #b0b0b5; --ink-3: #86868b; --line: #2a2a2d; --line-soft: #212123;
    --bg: #000000; --bg-alt: #0e0e10; --accent: #2997ff; --accent-press: #61b0ff;
    --accent-tint: rgba(41,151,255,0.16);
  }
  body { background: var(--bg); }
  .site-header { background: rgba(0,0,0,0.7); border-bottom-color: rgba(255,255,255,0.08); }
  .brand .mono { background: #f5f5f7; color: #000; }
  .trust { background: #000; }
  .tile { background: #0e0e10; border-color: rgba(255,255,255,0.08); }
  .band .tile { background: #141416; box-shadow: none; }
  .btn-secondary { background: rgba(255,255,255,0.10); color: var(--ink); }
  .btn-secondary:hover { background: rgba(255,255,255,0.16); }
  .work a { background: rgba(255,255,255,0.08); color: var(--ink); }
  .work a:hover { background: rgba(255,255,255,0.14); }
  .band-dark { background: #0e0e10; }
  .callbar { background: rgba(0,0,0,0.82); border-top-color: rgba(255,255,255,0.1); }
  .hero::before { background: radial-gradient(720px 400px at 50% 0%, rgba(41,151,255,0.14), rgba(41,151,255,0) 62%); }
}