/* ===== NovaTech 单页多语言站 · 样式 ===== */
:root {
  --brand: #1f6feb;
  --brand-dark: #134a9e;
  --ink: #1a2233;
  --muted: #5b6678;
  --line: #e3e8f0;
  --bg: #ffffff;
  --bg-alt: #f5f8fc;
  --radius: 14px;
  --shadow: 0 10px 30px rgba(20, 40, 80, .08);
  --maxw: 1140px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  font-family: "Segoe UI", system-ui, -apple-system, "PingFang SC", "Microsoft YaHei", Roboto, Arial, sans-serif;
  color: var(--ink);
  background: var(--bg);
  line-height: 1.65;
}
img, svg, canvas, video { max-width: 100%; display: block; }
a { color: var(--brand); text-decoration: none; }
.container { width: 100%; max-width: var(--maxw); margin: 0 auto; padding: 0 22px; }

/* ===== Header / Nav ===== */
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: rgba(255, 255, 255, .92);
  backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--line);
}
.nav-wrap { display: flex; align-items: center; gap: 18px; height: 64px; }
.brand { display: flex; align-items: center; gap: 10px; font-weight: 700; color: var(--ink); }
.brand-mark {
  width: 32px; height: 32px; border-radius: 8px;
  background: linear-gradient(135deg, var(--brand), var(--brand-dark));
  color: #fff; display: grid; place-items: center; font-weight: 800;
}
.brand-name { font-size: 16px; }
.nav { display: flex; gap: 22px; margin-left: auto; }
.nav a { color: var(--muted); font-weight: 600; font-size: 14px; transition: color .2s; }
.nav a:hover { color: var(--brand); }
.nav-right { display: flex; align-items: center; gap: 12px; margin-left: 18px; }
.lang-select {
  border: 1px solid var(--line); border-radius: 8px; padding: 6px 10px;
  font-size: 13px; background: #fff; color: var(--ink); cursor: pointer;
}
.nav-toggle { display: none; border: 0; background: none; font-size: 22px; cursor: pointer; color: var(--ink); }

/* ===== Buttons ===== */
.btn {
  display: inline-block; padding: 11px 22px; border-radius: 999px;
  font-weight: 700; font-size: 14px; cursor: pointer; border: 1px solid transparent;
  transition: transform .12s ease, box-shadow .2s ease, background .2s;
}
.btn:active { transform: translateY(1px); }
.btn-primary { background: var(--brand); color: #fff; box-shadow: 0 8px 20px rgba(31,111,235,.25); }
.btn-primary:hover { background: var(--brand-dark); }
.btn-ghost { background: #fff; color: var(--brand); border-color: var(--line); }
.btn-ghost:hover { border-color: var(--brand); }

/* ===== Hero ===== */
.hero {
  background: radial-gradient(1200px 500px at 70% -10%, #e9f2ff 0%, transparent 60%),
              linear-gradient(160deg, #0e2a5e 0%, #1f6feb 100%);
  color: #fff; text-align: center; padding: 96px 0 110px;
}
.hero h1 { font-size: clamp(28px, 5vw, 48px); margin: 0 0 14px; font-weight: 800; letter-spacing: .3px; }
.hero-sub { font-size: clamp(15px, 2.2vw, 20px); opacity: .92; margin: 0 0 30px; font-weight: 500; }
.hero .btn-primary { background: #fff; color: var(--brand); box-shadow: 0 10px 30px rgba(0,0,0,.18); }

/* ===== Sections ===== */
.section { padding: 80px 0; }
.section-alt { background: var(--bg-alt); }
.section-title { text-align: center; font-size: clamp(24px, 3.4vw, 34px); margin: 0 0 10px; font-weight: 800; }
.section-lead { text-align: center; color: var(--muted); max-width: 720px; margin: 0 auto 40px; font-size: 16px; }

/* ===== About ===== */
.about-grid { display: grid; grid-template-columns: 1.4fr 1fr; gap: 40px; align-items: center; }
.about-text p { color: var(--muted); margin: 0 0 16px; }
.stats { list-style: none; padding: 0; margin: 0; display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
.stats li {
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius);
  padding: 18px; text-align: center; box-shadow: var(--shadow);
}
.stats .num { font-size: 28px; font-weight: 800; color: var(--brand); display: block; }
.stats .lbl { font-size: 13px; color: var(--muted); }

/* ===== Video ===== */
.video-frame { max-width: 880px; margin: 0 auto; border-radius: var(--radius); overflow: hidden; box-shadow: var(--shadow); background: #000; }
.video-frame video { width: 100%; aspect-ratio: 16/9; object-fit: cover; }

/* ===== Cards (products & certs) ===== */
.card-grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 24px; }
.card {
  background: #fff; border: 1px solid var(--line); border-radius: var(--radius);
  overflow: hidden; box-shadow: var(--shadow); transition: transform .18s ease, box-shadow .18s ease;
  display: flex; flex-direction: column;
}
.card:hover { transform: translateY(-6px); box-shadow: 0 18px 40px rgba(20,40,80,.14); }
.card .thumb { aspect-ratio: 4/3; background: var(--bg-alt); }
.card .thumb img { width: 100%; height: 100%; object-fit: cover; }
.card .body { padding: 16px 18px 20px; }
.card h3 { margin: 0 0 8px; font-size: 17px; }
.card p { margin: 0; color: var(--muted); font-size: 14px; }
.cert-grid { grid-template-columns: repeat(4, 1fr); }
.cert-grid .card .thumb { aspect-ratio: 1/1; padding: 18px; }
.cert-grid .card .thumb img { object-fit: contain; }

/* ===== Flipbook ===== */
.flipbook { max-width: 760px; margin: 0 auto; }
.flip-stage {
  position: relative; background: #fff; border: 1px solid var(--line);
  border-radius: var(--radius); box-shadow: var(--shadow); overflow: hidden;
  display: grid; place-items: center; min-height: 480px; padding: 14px;
}
#flip-canvas { width: 100%; height: auto; box-shadow: 0 6px 18px rgba(0,0,0,.12); transition: transform .4s ease; }
#flip-canvas.flip-anim { transform: rotateY(-12deg) scale(.98); }
.flip-loading { position: absolute; color: var(--muted); font-size: 15px; }
.flip-controls { display: flex; align-items: center; justify-content: center; gap: 14px; margin-top: 20px; flex-wrap: wrap; }
.flip-page { font-weight: 700; color: var(--ink); min-width: 90px; text-align: center; }

/* ===== Contact ===== */
.contact-wrap { max-width: 720px; }
.contact-form { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; }
.field { display: flex; flex-direction: column; gap: 6px; }
.field-wide { grid-column: 1 / -1; }
.field label { font-size: 13px; font-weight: 700; color: var(--muted); }
.field input, .field textarea {
  border: 1px solid var(--line); border-radius: 10px; padding: 11px 13px;
  font: inherit; color: var(--ink); background: #fff; resize: vertical;
}
.field input:focus, .field textarea:focus { outline: 2px solid var(--brand); border-color: var(--brand); }
.form-note { font-size: 12px; color: var(--muted); margin: 12px 0 0; }
.form-status { grid-column: 1 / -1; min-height: 22px; font-weight: 600; margin: 4px 0 0; }
.form-status.ok { color: #1a9d54; }
.form-status.err { color: #d23b3b; }

/* ===== Footer ===== */
.site-footer { background: #0e1b33; color: #c8d2e6; padding: 54px 0 0; }
.footer-grid { display: grid; grid-template-columns: 2fr 1fr 1fr; gap: 30px; padding-bottom: 30px; }
.site-footer .brand { color: #fff; }
.footer-addr { color: #9fb0cc; font-size: 14px; }
.site-footer h4 { color: #fff; margin: 0 0 14px; font-size: 15px; }
.footer-links { list-style: none; padding: 0; margin: 0; }
.footer-links li { margin-bottom: 8px; }
.footer-links a { color: #9fb0cc; }
.footer-links a:hover { color: #fff; }
.social { display: flex; gap: 10px; }
.social a {
  width: 38px; height: 38px; border-radius: 50%; background: #1c2c4d; color: #fff;
  display: grid; place-items: center; font-weight: 700; transition: background .2s;
}
.social a:hover { background: var(--brand); }
.footer-bottom { border-top: 1px solid #1c2c4d; padding: 18px 22px; font-size: 13px; color: #8ea0c0; }

/* ===== Responsive ===== */
@media (max-width: 880px) {
  .nav { display: none; position: absolute; top: 64px; left: 0; right: 0;
    flex-direction: column; background: #fff; border-bottom: 1px solid var(--line); padding: 14px 22px; gap: 14px; }
  .nav.open { display: flex; }
  .nav-toggle { display: block; }
  .about-grid { grid-template-columns: 1fr; }
  .card-grid { grid-template-columns: repeat(2, 1fr); }
  .cert-grid { grid-template-columns: repeat(2, 1fr); }
  .contact-form { grid-template-columns: 1fr; }
  .footer-grid { grid-template-columns: 1fr; }
}
@media (max-width: 520px) {
  .card-grid, .cert-grid, .stats { grid-template-columns: 1fr; }
  .section { padding: 60px 0; }
}