:root {
  color-scheme: light dark;
  --bg: #f6f7fb;
  --surface: #ffffff;
  --surface-soft: #eef0f6;
  --text: #0a0d17;
  --muted: #596170;
  --line: #d9dee8;
  /* Echo Cyan(#00D1F2)은 밝은 배경 위 텍스트/버튼엔 대비가 부족해, 라이트 모드 전용으로
     안드로이드 앱의 라이트 팔레트(EchoTheme.kt LightColors.primary)와 동일하게 어둡힌 값을 쓴다. */
  --primary: #006e82;
  --primary-soft: #c9f3fb;
  --secondary: #3a5fa8;
  --accent: #b96a00;
  --max: 1080px;
  font-family: Inter, Pretendard, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body { margin: 0; background: var(--bg); color: var(--text); line-height: 1.68; }
a { color: var(--primary); text-underline-offset: 3px; }
img { max-width: 100%; height: auto; }

.skip-link { position: absolute; left: -9999px; top: 0; }
.skip-link:focus { left: 16px; top: 16px; z-index: 10; padding: 10px 14px; background: var(--surface); }

header { border-bottom: 1px solid var(--line); background: color-mix(in srgb, var(--bg) 88%, transparent); }
.nav { max-width: var(--max); margin: 0 auto; padding: 18px 24px; display: flex; gap: 24px; align-items: center; }
.brand { display: inline-flex; gap: 10px; align-items: center; color: var(--text); text-decoration: none; font-size: 1.35rem; font-weight: 800; letter-spacing: -0.04em; }
.brand img { width: 34px; height: 34px; border-radius: 9px; }
.nav-links { margin-left: auto; display: flex; flex-wrap: wrap; gap: 16px; align-items: center; }
.nav-links a { color: var(--muted); text-decoration: none; font-size: .95rem; }
.nav-links a:hover, .nav-links a[aria-current="page"] { color: var(--text); }

main { max-width: var(--max); margin: 0 auto; padding: 56px 24px 96px; }
.hero { display: grid; grid-template-columns: 1.15fr .85fr; align-items: center; gap: 56px; min-height: 520px; }
.eyebrow { color: var(--primary); font-weight: 760; letter-spacing: .04em; text-transform: uppercase; font-size: .82rem; }
h1, h2, h3 { line-height: 1.18; letter-spacing: -.04em; }
h1 { font-size: clamp(2.7rem, 7vw, 5.6rem); margin: 12px 0 22px; }
h2 { font-size: clamp(1.7rem, 4vw, 2.6rem); margin: 52px 0 18px; }
h3 { font-size: 1.18rem; margin: 28px 0 8px; }
.lede { max-width: 700px; font-size: 1.16rem; color: var(--muted); }
.hero-card { padding: 24px; border-radius: 32px; background: linear-gradient(145deg, #0a0d17, #13253d); box-shadow: 0 28px 80px rgba(10, 13, 23, .22); }
.hero-card img { display: block; border-radius: 20px; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 30px; }
.button { display: inline-flex; align-items: center; justify-content: center; min-height: 46px; padding: 0 18px; border-radius: 999px; text-decoration: none; font-weight: 750; background: var(--primary); color: #fff; }
.button.secondary { background: var(--surface-soft); color: var(--text); }
.grid { display: grid; grid-template-columns: repeat(3, 1fr); gap: 18px; }
.card { padding: 24px; border: 1px solid var(--line); border-radius: 24px; background: var(--surface); }
.card h3 { margin-top: 0; }
.card p { color: var(--muted); margin-bottom: 0; }
.notice { margin: 28px 0; padding: 18px 20px; border-left: 4px solid var(--primary); border-radius: 8px 18px 18px 8px; background: var(--surface-soft); }
.meta { color: var(--muted); font-size: .94rem; }
.legal { max-width: 820px; }
.legal h1 { font-size: clamp(2.4rem, 6vw, 4.4rem); }
.legal ul, .legal ol { padding-left: 1.35rem; }
.legal table { width: 100%; border-collapse: collapse; margin: 18px 0 28px; font-size: .94rem; }
.legal th, .legal td { padding: 12px; border: 1px solid var(--line); text-align: left; vertical-align: top; }
.legal th { background: var(--surface-soft); }
.toc { padding: 20px 24px; border-radius: 18px; background: var(--surface); border: 1px solid var(--line); }
.toc ol { columns: 2; }
.pillars { display: grid; grid-template-columns: repeat(4, 1fr); gap: 16px; }
.pillar { padding: 22px; border: 1px solid var(--line); border-radius: 20px; background: var(--surface); }
.pillar .num { font-size: .78rem; font-weight: 800; color: var(--muted); letter-spacing: .06em; }
.pillar h3 { margin: 10px 0 8px; font-size: 1.05rem; }
.pillar p { color: var(--muted); margin: 0; font-size: .94rem; }

.download { display: flex; flex-wrap: wrap; align-items: center; justify-content: space-between; gap: 28px; margin: 52px 0 0; padding: 36px; border-radius: 28px; background: linear-gradient(145deg, #0a0d17, #13253d); color: #fff; }
.download h2 { color: #fff; margin: 0 0 8px; }
.download p { color: rgba(255, 255, 255, .68); margin: 0; max-width: 460px; }
.store-badges { display: flex; flex-wrap: wrap; gap: 12px; }
.store-badge { display: inline-flex; align-items: center; gap: 10px; padding: 11px 20px; border-radius: 14px; background: #fff; color: #0a0d17; text-decoration: none; font-weight: 700; }
.store-badge .mark { font-size: 1.4rem; line-height: 1; }
.store-badge small { display: block; font-weight: 500; font-size: .72rem; color: #596170; }
.store-badge.disabled { background: rgba(255, 255, 255, .08); color: rgba(255, 255, 255, .55); pointer-events: none; }
.store-badge.disabled small { color: rgba(255, 255, 255, .4); }

.showcase { display: flex; align-items: center; gap: 56px; margin: 72px 0; }
.showcase.reverse { flex-direction: row-reverse; }
.showcase-media { flex: 0 0 280px; }
.showcase-media img { border-radius: 28px; box-shadow: 0 24px 60px rgba(10, 13, 23, .16); display: block; width: 100%; }
.showcase-media.watch img { width: 200px; margin: 0 auto; }
.showcase-text { flex: 1; }
.showcase-text h2 { margin-top: 0; }
.step-list { list-style: none; margin: 22px 0 0; padding: 0; display: grid; gap: 16px; }
.step-list li { display: grid; grid-template-columns: 30px 1fr; gap: 14px; }
.step-list .n { width: 30px; height: 30px; border-radius: 50%; background: var(--primary-soft); color: var(--primary); font-weight: 800; font-size: .85rem; display: flex; align-items: center; justify-content: center; }
.step-list strong { display: block; margin-bottom: 2px; }
.step-list span { color: var(--muted); font-size: .95rem; }
.guide-hero { max-width: 760px; }

footer { border-top: 1px solid var(--line); }
.footer-inner { max-width: var(--max); margin: 0 auto; padding: 28px 24px 42px; display: flex; flex-wrap: wrap; gap: 12px 24px; color: var(--muted); font-size: .9rem; }
.footer-inner nav { margin-left: auto; display: flex; flex-wrap: wrap; gap: 14px; }

@media (max-width: 760px) {
  .nav { align-items: flex-start; }
  .nav-links { gap: 10px 14px; }
  .hero { grid-template-columns: 1fr; min-height: auto; gap: 34px; }
  .hero-card { order: -1; }
  .grid { grid-template-columns: 1fr; }
  .pillars { grid-template-columns: 1fr 1fr; }
  .download { flex-direction: column; align-items: flex-start; }
  .showcase, .showcase.reverse { flex-direction: column; gap: 28px; }
  .showcase-media { flex: 0 0 auto; width: 220px; }
  .toc ol { columns: 1; }
  .legal table { display: block; overflow-x: auto; }
  .footer-inner nav { width: 100%; margin-left: 0; }
}

@media (max-width: 520px) {
  .pillars { grid-template-columns: 1fr; }
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0a0d17;
    --surface: #10131c;
    --surface-soft: #181c28;
    --text: #ffffff;
    --muted: #b2bac8;
    --line: #2a2f3c;
    /* 다크는 "제품 기본" 모드라 브랜드 색상을 원본 그대로 쓴다 — Echo Cyan / Return Blue / Energy. */
    --primary: #00d1f2;
    --primary-soft: #163540;
    --secondary: #598cff;
    --accent: #ff9933;
  }
  .button { color: #00252c; }
  .button.secondary { color: var(--text); }
}