/* =========================================================
   Starter Kit — 공통 스타일시트
   - 반응형(clamp 타이포) · 디자인 토큰(CSS 변수)
   - 모바일 햄버거 메뉴(검증된 패턴: backdrop-filter 함정 회피, 불투명 패널)
   ========================================================= */

:root {
  /* 색상 (여기만 바꾸면 사이트 전체 톤이 바뀜) */
  --color-bg: #ffffff;
  --color-bg-alt: #f6f7f9;
  --color-text: #14161a;
  --color-text-soft: #565b63;
  --color-text-mute: #8b9099;
  --color-line: #e6e8ec;
  --color-accent: #3b6fff;
  --color-accent-deep: #2b54cc;

  --font-sans: -apple-system, BlinkMacSystemFont, 'Apple SD Gothic Neo',
    'Segoe UI', Roboto, 'Helvetica Neue', Arial, 'Malgun Gothic', sans-serif;

  --max-w: 1160px;
  --pad: clamp(20px, 5vw, 56px);
  --radius: 12px;
  --header-h: 68px;

  --ease: cubic-bezier(0.65, 0.05, 0.36, 1);
  --t-fast: 0.22s;
  --t-mid: 0.4s;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  font-family: var(--font-sans);
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
}
img, svg, video { max-width: 100%; height: auto; display: block; }
a { color: inherit; text-decoration: none; }
button { font-family: inherit; cursor: pointer; border: none; background: none; }
ul { margin: 0; padding: 0; list-style: none; }
h1, h2, h3 { margin: 0; font-weight: 750; letter-spacing: -0.02em; line-height: 1.15; }
p { margin: 0; }

/* ---------- 레이아웃 ---------- */
.container { width: 100%; max-width: var(--max-w); margin: 0 auto; padding: 0 var(--pad); }
.section { padding: clamp(56px, 8vw, 110px) 0; }
.eyebrow {
  display: inline-block; font-size: 13px; letter-spacing: 0.14em; text-transform: uppercase;
  color: var(--color-accent); font-weight: 650; margin-bottom: 14px;
}

/* ---------- 버튼 ---------- */
.btn {
  display: inline-flex; align-items: center; gap: 8px;
  padding: 14px 26px; border-radius: 999px; font-weight: 600; font-size: 15px;
  transition: transform var(--t-fast), background var(--t-fast), color var(--t-fast);
  border: 1px solid transparent;
}
.btn-primary { background: var(--color-accent); color: #fff; }
.btn-primary:hover { background: var(--color-accent-deep); transform: translateY(-2px); }
.btn-ghost { border-color: var(--color-line); color: var(--color-text); }
.btn-ghost:hover { background: var(--color-bg-alt); }

/* ---------- 헤더 / 내비 ---------- */
.site-header {
  position: fixed; top: 0; left: 0; right: 0; z-index: 100;
  background: rgba(255,255,255,0.85);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--color-line);
}
.header-inner { display: flex; align-items: center; justify-content: space-between; height: var(--header-h); }
.brand { display: flex; align-items: center; gap: 9px; font-weight: 800; font-size: 20px; letter-spacing: -0.03em; }
.brand-mark {
  width: 28px; height: 28px; border-radius: 7px; display: grid; place-items: center;
  background: linear-gradient(135deg, var(--color-accent), #6f9bff);
  color: #fff; font-size: 14px; font-weight: 800;
}
.nav { display: flex; align-items: center; gap: 32px; }
.nav-list { display: flex; gap: 26px; }
.nav-list a { font-size: 15px; font-weight: 500; color: var(--color-text); padding: 6px 0; transition: color var(--t-fast); }
.nav-list a:hover, .nav-list a.active { color: var(--color-accent); }
.nav-cta { background: var(--color-text); color: #fff; padding: 10px 18px; border-radius: 999px; font-size: 14px; font-weight: 600; }
.nav-cta:hover { background: var(--color-accent); }

.menu-toggle { display: none; width: 30px; height: 30px; position: relative; }
.menu-toggle span {
  position: absolute; left: 4px; right: 4px; height: 2px; background: var(--color-text);
  transition: transform var(--t-fast), opacity var(--t-fast), top var(--t-fast);
}
.menu-toggle span:nth-child(1) { top: 9px; }
.menu-toggle span:nth-child(2) { top: 15px; }
.menu-toggle span:nth-child(3) { top: 21px; }
.menu-toggle.open span:nth-child(1) { top: 15px; transform: rotate(45deg); }
.menu-toggle.open span:nth-child(2) { opacity: 0; }
.menu-toggle.open span:nth-child(3) { top: 15px; transform: rotate(-45deg); }

/* ---------- 히어로 ---------- */
.hero { padding: calc(var(--header-h) + clamp(48px, 9vw, 120px)) 0 clamp(48px, 9vw, 120px); background: var(--color-bg-alt); }
.hero h1 { font-size: clamp(34px, 6vw, 68px); margin-bottom: 20px; }
.hero p { font-size: clamp(16px, 1.8vw, 19px); color: var(--color-text-soft); max-width: 560px; margin-bottom: 30px; }
.hero .actions { display: flex; gap: 12px; flex-wrap: wrap; }

/* ---------- 기능 카드 ---------- */
.features { display: grid; grid-template-columns: repeat(3, 1fr); gap: 22px; }
.card { padding: 28px; border: 1px solid var(--color-line); border-radius: var(--radius); background: #fff; }
.card h3 { font-size: 19px; margin-bottom: 10px; }
.card p { color: var(--color-text-soft); font-size: 15px; }

/* ---------- 푸터 ---------- */
.site-footer { border-top: 1px solid var(--color-line); padding: 44px 0; color: var(--color-text-mute); font-size: 14px; }
.site-footer .footer-inner { display: flex; justify-content: space-between; gap: 20px; flex-wrap: wrap; }

/* ---------- 등장 애니메이션 ---------- */
.reveal { opacity: 0; transform: translateY(22px); transition: opacity 0.7s var(--ease), transform 0.7s var(--ease); }
.reveal.in { opacity: 1; transform: translateY(0); }

/* =====================  반응형  ===================== */
@media (max-width: 860px) { .features { grid-template-columns: 1fr; } }

@keyframes navIn { from { opacity: 0; transform: translateY(-8px); } to { opacity: 1; transform: translateY(0); } }
@media (prefers-reduced-motion: reduce) { .nav.open nav, .nav.open .nav-cta { animation: none; } }

@media (max-width: 720px) {
  .nav { display: none; }
  .menu-toggle { display: block; }

  /* 모바일에선 헤더 backdrop-filter 제거: fixed 메뉴 패널이 헤더 안에 갇히는
     (Safari 한 프레임 깜빡임) 문제를 원천 차단 */
  .site-header { backdrop-filter: none; -webkit-backdrop-filter: none; }
  .site-header.nav-active { background: #fff; }

  .nav.open {
    display: flex; position: fixed; inset: var(--header-h) 0 0 0;
    background: #fff;                 /* 첫 프레임부터 불투명 → 콘텐츠 비침 없음 */
    flex-direction: column; align-items: flex-start; justify-content: flex-start;
    gap: 24px; padding: 36px var(--pad); z-index: 99; overflow-y: auto;
  }
  /* 패널은 즉시 불투명, 안쪽 항목만 한 덩어리로 부드럽게 등장 */
  .nav.open nav, .nav.open .nav-cta { will-change: opacity, transform; animation: navIn 0.22s var(--ease) both; }
  .nav.open nav { width: 100%; }
  .nav.open .nav-list { flex-direction: column; gap: 22px; width: 100%; }
  .nav.open .nav-list a { font-size: 22px; font-weight: 700; transition: none; }
  .nav.open .nav-cta { align-self: flex-start; }

  .hero .actions .btn { flex: 1 1 auto; justify-content: center; }
}

::selection { background: var(--color-accent); color: #fff; }