/* ============================================================
   PTMIND CN — 纯净展示型站点（用于 ICP 备案）
   ============================================================ */

:root {
  --ink:      #14181F;
  --paper:    #FFFFFF;
  --paper-2:  #F6F7F9;
  --signal:   #FF5A36;
  --circuit:  #3D6EF5;
  --mist:     #6B7280;
  --line:     #E7E9EE;
  --font: "Noto Sans SC", system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", sans-serif;
  --wrap: 1080px;
  --pad: clamp(1.25rem, 4vw, 2.5rem);
}

* { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }

body {
  font-family: var(--font);
  color: var(--ink);
  background: var(--paper);
  line-height: 1.75;
  -webkit-font-smoothing: antialiased;
}

.wrap { max-width: var(--wrap); margin-inline: auto; padding-inline: var(--pad); }
a { color: inherit; text-decoration: none; }

.skip-link { position: absolute; left: -999px; top: 0; z-index: 200; background: var(--ink); color: #fff; padding: .6rem 1rem; }
.skip-link:focus { left: 0; }
:focus-visible { outline: 2px solid var(--circuit); outline-offset: 3px; }

/* ---------- Brand ---------- */
.brand { display: inline-flex; align-items: center; gap: .55rem; }
.brand-mark {
  width: 18px; height: 18px; border-radius: 50%;
  background:
    radial-gradient(circle at 33% 42%, var(--signal) 0 4px, transparent 5px),
    radial-gradient(circle at 67% 58%, var(--circuit) 0 4px, transparent 5px);
  box-shadow: inset 0 0 0 1.5px var(--ink);
}
.brand-name { font-weight: 900; letter-spacing: -.02em; font-size: 1.15rem; }

/* ---------- Header ---------- */
.site-header {
  position: sticky; top: 0; z-index: 100;
  background: rgba(255,255,255,.9); backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.header-inner { display: flex; align-items: center; height: 64px; gap: 1.5rem; }
.nav { display: flex; gap: 1.8rem; margin-left: auto; font-size: .95rem; font-weight: 500; }
.nav a { color: var(--ink); padding: .2rem 0; border-bottom: 2px solid transparent; transition: border-color .2s; }
.nav a:hover { border-color: var(--signal); }

/* ---------- Hero ---------- */
.hero { border-bottom: 1px solid var(--line); }
.hero-inner { padding-top: clamp(3.5rem, 10vw, 6.5rem); padding-bottom: clamp(3.5rem, 10vw, 6.5rem); }
.hero-title {
  font-weight: 900; letter-spacing: -.02em; line-height: 1.25;
  font-size: clamp(1.9rem, 5.5vw, 3.4rem); max-width: 18ch;
}
.hero-sub { margin-top: 1.2rem; font-size: clamp(1.05rem, 2vw, 1.3rem); color: var(--mist); }

/* ---------- Sections ---------- */
.section { padding-top: clamp(3rem, 8vw, 5rem); padding-bottom: clamp(3rem, 8vw, 5rem); }
.section-alt { background: var(--paper-2); border-block: 1px solid var(--line); }
.eyebrow { font-size: .82rem; letter-spacing: .18em; text-transform: uppercase; color: var(--signal); font-weight: 700; margin-bottom: .7rem; }
.section-title { font-weight: 900; letter-spacing: -.02em; font-size: clamp(1.5rem, 3.5vw, 2.3rem); line-height: 1.3; }
.prose { margin-top: 1.4rem; max-width: 60ch; color: #374151; }
.prose p + p { margin-top: 1rem; }

/* ---------- Business cards ---------- */
.cards { display: grid; grid-template-columns: repeat(3, 1fr); gap: 1.25rem; margin-top: 2.2rem; }
.card { background: var(--paper); border: 1px solid var(--line); border-radius: 14px; padding: 1.6rem; }
.card-tag { font-size: .74rem; letter-spacing: .08em; text-transform: uppercase; color: var(--mist); font-weight: 700; }
.card-name { font-weight: 900; font-size: 1.5rem; letter-spacing: -.02em; margin-top: .4rem; }
.card-desc { margin-top: .8rem; color: #374151; font-size: .95rem; }

/* ---------- Contact ---------- */
.contact-details { margin-top: 2rem; display: grid; grid-template-columns: repeat(2, minmax(0,1fr)); gap: 1.4rem 2.5rem; max-width: 640px; }
.contact-details dt { font-size: .78rem; letter-spacing: .08em; text-transform: uppercase; color: var(--mist); font-weight: 700; }
.contact-details dd { margin-top: .25rem; font-size: 1.05rem; }
.contact-details dd a { border-bottom: 1px solid var(--line); }
.contact-details dd a:hover { border-color: var(--signal); color: var(--signal); }

/* ---------- Footer ---------- */
.site-footer { background: var(--ink); color: #C9CED8; }
.footer-inner {
  display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: .6rem;
  padding-top: 1.6rem; padding-bottom: 1.6rem; font-size: .85rem;
}
.footer-icp:hover { color: #fff; }

/* ---------- Responsive ---------- */
@media (max-width: 820px) {
  .cards { grid-template-columns: 1fr; }
}
@media (max-width: 560px) {
  .nav { gap: 1.1rem; font-size: .88rem; }
  .brand-name { font-size: 1rem; }
  .contact-details { grid-template-columns: 1fr; }
  .footer-inner { justify-content: flex-start; }
}