:root {
  --accent: #6366f1; --accent-2: #8b5cf6; --danger: #e5484d;
  --radius: 16px;
  --bg: #16181d; --surface: #1d2026; --text: #e7e9ee; --muted: #868c9a; --border: #2a2e37;
}
@media (prefers-color-scheme: light) {
  :root { --bg: #f7f6f4; --surface: #fff; --text: #23262f; --muted: #8b909c; --border: #ececef; }
}
* { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Noto Sans KR", sans-serif; line-height: 1.6; }
.nav { display: flex; justify-content: space-between; align-items: center; padding: 16px 24px; }
.nav-actions { display: flex; gap: 12px; align-items: center; }
.brand { font-weight: 700; font-size: 20px; }
.btn { display: inline-block; padding: 10px 18px; border-radius: var(--radius); text-decoration: none; font-weight: 600; cursor: pointer; border: none; }
.btn-primary { background: linear-gradient(135deg, var(--accent), var(--accent-2)); color: #fff; }
#lang-toggle { background: transparent; color: var(--text); border: 1px solid var(--border); border-radius: var(--radius); padding: 8px 12px; cursor: pointer; }

.section { max-width: 960px; margin: 0 auto; padding: 64px 24px; }
.hero { max-width: 800px; margin: 0 auto; padding: 80px 24px 48px; text-align: center; }
.hero h1 { font-size: clamp(28px, 5vw, 48px); line-height: 1.2; margin: 0 0 16px;
  background: linear-gradient(135deg, var(--accent), var(--accent-2)); -webkit-background-clip: text; background-clip: text; color: transparent; }
.hero .sub { font-size: clamp(16px, 2.5vw, 20px); color: var(--muted); margin: 0 0 32px; }
.btn-lg { padding: 14px 28px; font-size: 18px; }
.contrast-row { display: flex; gap: 16px; align-items: center; justify-content: center; flex-wrap: wrap; }
.contrast-card { flex: 1; min-width: 220px; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 24px; }
.accent-card { border-color: var(--accent); }
.tag { font-weight: 700; margin-bottom: 8px; }
.accent-card .tag { color: var(--accent); }
.arrow { font-size: 28px; color: var(--muted); }
h2 { text-align: center; font-size: clamp(22px, 4vw, 32px); }

.mode { display: flex; gap: 40px; align-items: center; margin: 48px 0; }
.mode.reverse { flex-direction: row-reverse; }
.mode > div:last-child { flex: 1; }
.mode h3 { margin-top: 0; font-size: 22px; }

/* UI mockups (replace raw screenshots) */
.ui-mock { width: 50%; max-width: 440px; flex: none; background: var(--surface); border: 1px solid var(--border);
  border-radius: var(--radius); box-shadow: var(--shadow); overflow: hidden; }
.mock-head { display: flex; align-items: center; gap: 8px; padding: 12px 16px; font-size: 13px; font-weight: 600;
  color: var(--muted); border-bottom: 1px solid var(--border); }
.mock-head .dot { width: 8px; height: 8px; border-radius: 50%; background: linear-gradient(135deg, var(--accent), var(--accent-2)); }
.mock-body { padding: 16px; display: flex; flex-direction: column; gap: 10px; }

/* chat */
.bubble { max-width: 80%; padding: 10px 14px; border-radius: 14px; font-size: 14px; line-height: 1.5; }
.bubble.coach { align-self: flex-start; background: color-mix(in srgb, var(--accent) 14%, var(--surface)); border: 1px solid var(--border); border-bottom-left-radius: 4px; }
.bubble.me { align-self: flex-end; background: linear-gradient(135deg, var(--accent), var(--accent-2)); color: #fff; border-bottom-right-radius: 4px; }
.mock-input { display: flex; align-items: center; justify-content: space-between; gap: 8px; margin: 0 16px 16px;
  padding: 10px 14px; border: 1px solid var(--border); border-radius: 12px; color: var(--muted); font-size: 14px; }
.mock-input .mic { font-size: 16px; }

/* shadowing */
.line { display: flex; align-items: center; gap: 10px; padding: 10px 12px; border-radius: 10px; font-size: 14px; color: var(--muted); }
.line .ts { font-variant-numeric: tabular-nums; font-size: 12px; opacity: 0.7; flex: none; }
.line.active { background: color-mix(in srgb, var(--accent) 16%, var(--surface)); color: var(--text); font-weight: 600; border: 1px solid var(--accent); }
.line .play { margin-left: auto; color: var(--accent); }
.feature-list { list-style: none; padding: 0; max-width: 640px; margin: 24px auto; }
.feature-list li { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 16px 20px; margin-bottom: 12px; }
.works { text-align: center; }
@media (max-width: 640px) {
  .mode, .mode.reverse { flex-direction: column; }
  .ui-mock { width: 100%; max-width: 100%; }
}

.cta-note { color: var(--muted); font-size: 14px; margin: 12px 0 0; }
.steps { list-style: none; padding: 0; max-width: 640px; margin: 24px auto; counter-reset: step; }
.steps li { display: flex; align-items: center; gap: 16px; padding: 16px 0; }
.step-num { flex: none; width: 36px; height: 36px; display: grid; place-items: center; border-radius: 50%;
  background: linear-gradient(135deg, var(--accent), var(--accent-2)); color: #fff; font-weight: 700; }

.footer { display: flex; gap: 24px; justify-content: center; padding: 40px 24px; border-top: 1px solid var(--border); color: var(--muted); }
.footer a { color: var(--muted); text-decoration: none; }
.footer a:hover { color: var(--text); }