/* ============================================================
   Mandarin Masterclass — Full Onboard Guide
   Follows the Sifu Kairesh ink-brush design language:
   cream paper, ink black, seal-stamp vermillion, brushed gold.
   ============================================================ */

:root {
  --ink: #1c1a17;
  --ink-soft: #3a3530;
  --paper: #f8f3e8;
  --paper-dim: #efe6d3;
  --vermillion: #a3121a;
  --vermillion-dark: #7c0d13;
  --gold: #c9a24b;
  --gold-soft: #e4d3a0;
  --line: rgba(28, 26, 23, 0.12);
  --shadow: 0 20px 50px rgba(28, 26, 23, 0.12);
  --radius: 6px;
  --serif: "Noto Serif TC", Georgia, serif;
  --sans: "Inter", -apple-system, BlinkMacSystemFont, sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  font-family: var(--sans);
  color: var(--ink);
  background: var(--paper);
  line-height: 1.65;
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }

a { color: inherit; text-decoration: none; }

h1, h2, h3 {
  font-family: var(--serif);
  font-weight: 700;
  line-height: 1.15;
  margin: 0 0 0.5em;
  letter-spacing: 0.01em;
}

p { margin: 0 0 1em; }

.container {
  width: 100%;
  max-width: 980px;
  margin: 0 auto;
  padding: 0 24px;
}

.accent { color: var(--vermillion); }

.eyebrow {
  text-transform: uppercase;
  letter-spacing: 0.25em;
  font-size: 0.78rem;
  font-weight: 600;
  color: var(--gold);
  margin-bottom: 8px;
}

.section-sub {
  color: var(--ink-soft);
  max-width: 560px;
  margin: 0 auto 28px;
}

/* ---------- Hero ---------- */

.hero {
  text-align: center;
  padding: 56px 0 64px;
  background:
    radial-gradient(ellipse at top, rgba(201, 162, 75, 0.12), transparent 60%),
    var(--paper);
  border-bottom: 1px solid var(--line);
}

.hero-logo {
  width: 150px;
  height: auto;
  margin: 0 auto 24px;
}

.hero h1 {
  font-size: clamp(1.8rem, 4.5vw, 2.8rem);
  max-width: 720px;
  margin-left: auto;
  margin-right: auto;
}

.hero-sub {
  color: var(--ink-soft);
  max-width: 580px;
  margin: 0 auto 36px;
}

/* ---------- Responsive video ---------- */

.video-frame {
  position: relative;
  max-width: 760px;
  margin: 0 auto;
  aspect-ratio: 16 / 9;
  background: var(--ink);
  border-radius: var(--radius);
  overflow: hidden;
  box-shadow: var(--shadow);
}

.video-frame iframe {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  border: 0;
}

/* ---------- Onboarding steps ---------- */

.steps {
  padding: 64px 0;
  text-align: center;
}

.steps h2 { font-size: clamp(1.5rem, 3.5vw, 2.1rem); }

.step-list {
  list-style: none;
  margin: 0 auto;
  padding: 0;
  max-width: 640px;
  text-align: left;
}

.step-list li {
  display: flex;
  align-items: center;
  gap: 18px;
  background: #fffdf8;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: 18px 22px;
  margin-bottom: 14px;
  box-shadow: 0 6px 18px rgba(28, 26, 23, 0.05);
}

.step-num {
  flex: 0 0 auto;
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  border-radius: 50%;
  background: var(--vermillion);
  color: var(--paper);
  font-family: var(--serif);
  font-size: 1.25rem;
  font-weight: 700;
}

.step-list h3 {
  font-family: var(--sans);
  font-size: 1.02rem;
  font-weight: 600;
  margin: 0;
  line-height: 1.4;
}

.step-link {
  color: var(--vermillion);
  border-bottom: 1px solid var(--gold-soft);
  white-space: nowrap;
}

.step-link:hover { color: var(--vermillion-dark); }

/* ---------- Device quick nav ---------- */

.device-nav {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(248, 243, 232, 0.94);
  backdrop-filter: blur(6px);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  padding: 14px 0;
  text-align: center;
}

.device-nav-label {
  margin: 0 0 8px;
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.2em;
  color: var(--ink-soft);
}

.device-nav-links {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 8px;
}

.device-nav-links a {
  padding: 6px 16px;
  border: 1px solid var(--line);
  border-radius: 999px;
  font-size: 0.9rem;
  font-weight: 500;
  background: #fffdf8;
  transition: all 0.2s ease;
}

.device-nav-links a:hover,
.device-nav-links a.is-active {
  background: var(--vermillion);
  border-color: var(--vermillion);
  color: var(--paper);
}

/* ---------- Device sections ---------- */

.device {
  padding: 64px 0;
  text-align: center;
  scroll-margin-top: 110px;
}

.device:nth-of-type(even) { background: var(--paper-dim); }

.device h2 {
  font-size: clamp(1.5rem, 3.5vw, 2.1rem);
  margin-bottom: 28px;
}

.guide-images {
  display: grid;
  gap: 24px;
  max-width: 760px;
  margin: 0 auto;
}

.guide-images img {
  width: 100%;
  height: auto;
  border-radius: var(--radius);
  border: 1px solid var(--line);
  box-shadow: var(--shadow);
  background: #fff;
}

.device-pc { border-top: 1px solid var(--line); }

/* ---------- Footer ---------- */

.page-footer {
  border-top: 1px solid var(--line);
  padding: 36px 0;
  text-align: center;
  color: var(--ink-soft);
  font-size: 0.92rem;
}

.page-footer .copyright {
  margin: 4px 0 0;
  font-size: 0.8rem;
  letter-spacing: 0.06em;
}

/* ---------- Responsive ---------- */

@media (max-width: 640px) {
  .hero { padding: 40px 0 48px; }
  .hero-logo { width: 120px; }
  .steps, .device { padding: 48px 0; }
  .step-list li { padding: 14px 16px; gap: 14px; }
  .step-num { width: 38px; height: 38px; font-size: 1.05rem; }
  .device { scroll-margin-top: 130px; }
}