/* QuaintAI — static site styles. Dark by default, light under prefers-color-scheme: light. */

:root {
  --bg:        #0d0f12;
  --bg-alt:    #111419;
  --surface:   #151920;
  --line:      #232932;
  --line-soft: #1b2028;
  --fg:        #e8eaed;
  --fg-strong: #ffffff;
  --fg-muted:  #9aa3ae;
  --fg-faint:  #6c7681;
  --accent:    #5fd3bc;
  --accent-dim:#2d6f63;
  --focus:     #8fe3d1;

  --font-sans: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue",
               "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", "Noto Sans CJK SC",
               "Source Han Sans SC", "WenQuanYi Micro Hei", Arial, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas,
               "Liberation Mono", monospace;

  --wrap: 62rem;
  --pad: 1.5rem;
}

@media (prefers-color-scheme: light) {
  :root {
    --bg:        #fbfaf8;
    --bg-alt:    #f2f1ed;
    --surface:   #ffffff;
    --line:      #ddd9d1;
    --line-soft: #e7e3dc;
    --fg:        #24282d;
    --fg-strong: #0f1216;
    --fg-muted:  #4f565e;
    --fg-faint:  #6b7078;
    --accent:    #0b6b5c;
    --accent-dim:#9ecdc3;
    --focus:     #0b6b5c;
  }
}

*, *::before, *::after { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font-family: var(--font-sans);
  font-size: 17px;
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* ---- bilingual visibility ---------------------------------------------- */
html[data-lang="zh"] body [lang="en"] { display: none; }
html[data-lang="en"] body [lang="zh"] { display: none; }

.wrap {
  width: 100%;
  max-width: var(--wrap);
  margin: 0 auto;
  padding: 0 var(--pad);
}

strong { color: var(--fg-strong); font-weight: 600; }

a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 3px; }

:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 3px;
  border-radius: 2px;
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--surface);
  color: var(--fg-strong);
  padding: .6rem 1rem;
  border: 1px solid var(--line);
  z-index: 10;
}
.skip-link:focus { left: 1rem; top: 1rem; }

/* ---- header ------------------------------------------------------------ */
.site-header {
  position: sticky;
  top: 0;
  z-index: 5;
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line-soft);
}
@supports not (backdrop-filter: blur(10px)) {
  .site-header { background: var(--bg); }
}

.header-row {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  min-height: 60px;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: .6rem;
  color: var(--fg-strong);
}
.brand:hover { text-decoration: none; }
.brand-mark {
  width: 10px; height: 10px;
  border-radius: 50%;
  background: var(--accent);
  flex: 0 0 auto;
}
.brand-name {
  font-weight: 600;
  letter-spacing: .02em;
  font-size: 1rem;
}

.lang-switch {
  display: inline-flex;
  align-items: center;
  gap: .35rem;
  font-size: .85rem;
}
.lang-btn {
  appearance: none;
  background: none;
  border: 0;
  padding: .3rem .35rem;
  margin: 0;
  color: var(--fg-faint);
  font: inherit;
  font-family: var(--font-mono);
  letter-spacing: .06em;
  cursor: pointer;
  border-bottom: 1px solid transparent;
  display: inline-block;
}
.lang-btn:hover { color: var(--fg); }
.lang-btn[aria-pressed="true"] {
  color: var(--fg-strong);
  border-bottom-color: var(--accent);
}
.lang-sep { color: var(--line); }

/* ---- hero -------------------------------------------------------------- */
.hero {
  padding: clamp(3.75rem, 11vw, 7.5rem) 0 clamp(2.75rem, 7vw, 4.75rem);
  border-bottom: 1px solid var(--line-soft);
}

.eyebrow {
  margin: 0 0 1.4rem;
  font-family: var(--font-mono);
  font-size: .76rem;
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--fg-faint);
}

.hero-title {
  margin: 0 0 1.5rem;
  font-size: clamp(2.4rem, 7vw, 3.8rem);
  line-height: 1.05;
  letter-spacing: -.02em;
  font-weight: 600;
  color: var(--fg-strong);
}

.hero-statement {
  margin: 0;
  max-width: 44ch;
  font-size: clamp(1.1rem, 2.4vw, 1.35rem);
  line-height: 1.6;
  color: var(--fg);
  text-wrap: pretty;
}
html[data-lang="en"] .hero-statement { max-width: 52ch; }

/* ---- sections ---------------------------------------------------------- */
.section {
  padding: clamp(3rem, 7.5vw, 5rem) 0;
  border-bottom: 1px solid var(--line-soft);
}
.section-alt { background: var(--bg-alt); }

.section-title {
  margin: 0 0 clamp(1.75rem, 4vw, 2.5rem);
  font-size: .8rem;
  font-weight: 600;
  letter-spacing: .18em;
  text-transform: uppercase;
  color: var(--fg-faint);
  font-family: var(--font-mono);
}

.lede {
  margin: 0 0 1.2rem;
  max-width: 56ch;
  font-size: clamp(1.02rem, 2vw, 1.18rem);
  line-height: 1.7;
  color: var(--fg);
}
.lede:last-child { margin-bottom: 0; }

/* ---- contact ----------------------------------------------------------- */
.contact-mail {
  margin: 0;
  font-size: 1rem;
}
.contact-mail a {
  color: var(--fg-muted);
  border-bottom: 1px solid var(--line);
  padding-bottom: 2px;
  word-break: break-word;
}
.contact-mail a:hover {
  color: var(--accent);
  border-bottom-color: var(--accent);
  text-decoration: none;
}

/* ---- legal pages ------------------------------------------------------- */
.doc { padding: clamp(2.5rem, 7vw, 4.5rem) 0 clamp(3rem, 8vw, 5rem); }
.doc-title {
  margin: 0 0 .75rem;
  font-size: clamp(1.8rem, 5vw, 2.5rem);
  line-height: 1.15;
  letter-spacing: -.02em;
  font-weight: 600;
  color: var(--fg-strong);
}
.doc-updated {
  margin: 0 0 clamp(2rem, 5vw, 2.75rem);
  font-family: var(--font-mono);
  font-size: .78rem;
  letter-spacing: .06em;
  color: var(--fg-faint);
}
.prose { max-width: 62ch; }
.prose h2 {
  margin: 2.5rem 0 .75rem;
  font-size: 1.08rem;
  font-weight: 600;
  color: var(--fg-strong);
  letter-spacing: -.005em;
}
.prose h2:first-child { margin-top: 0; }
.prose p { margin: 0 0 1.1rem; color: var(--fg-muted); }
.prose ul { margin: 0 0 1.1rem; padding-left: 1.25rem; }
.prose li { margin-bottom: .45rem; color: var(--fg-muted); }
.prose li::marker { color: var(--fg-faint); }
.prose a { word-break: break-word; }
.back-link { display: inline-block; margin-top: 2.5rem; font-size: .9rem; }

/* ---- footer ------------------------------------------------------------ */
.site-footer { padding: 2.5rem 0 3rem; }
.footer-row {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem 1.5rem;
}
.footer-brand {
  margin: 0 0 .5rem;
  font-weight: 600;
  color: var(--fg-muted);
  font-size: .9rem;
  letter-spacing: .02em;
}
.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: .5rem 1.5rem;
  font-size: .86rem;
}
.footer-links a { color: var(--fg-muted); }
.footer-links a:hover { color: var(--accent); }

/* ---- responsive -------------------------------------------------------- */
@media (max-width: 640px) {
  body { font-size: 16px; }
  :root { --pad: 1.25rem; }

}

@media print {
  .site-header, .skip-link { display: none; }
  body { background: #fff; color: #000; }
}