/* ==========================================================================
   전역 기반 — 리셋, 타이포, 레이아웃 프리미티브, 네비게이션, 푸터, 버튼
   ========================================================================== */

*, *::before, *::after { box-sizing: border-box; }
* { margin: 0; }

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 6rem; /* 고정 헤더에 가려지지 않도록 */
}

body {
  font-family: var(--font-sans);
  font-size: var(--t-base);
  line-height: var(--lh-body);
  color: var(--c-text);
  background-color: var(--c-abyss-1000);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden; /* 장식 요소가 가로 스크롤을 만들지 않게 */
}

img, svg, video { display: block; max-width: 100%; height: auto; }
button, input, textarea, select { font: inherit; color: inherit; }
ul, ol { list-style: none; padding: 0; }
a { color: inherit; text-decoration: none; }

/* ---- 포커스: 키보드 사용자에게만, 확실하게 보이도록 ---- */
:focus-visible {
  outline: 2px solid var(--c-signal);
  outline-offset: 3px;
  border-radius: var(--r-sharp);
}

::selection { background: var(--c-signal); color: var(--c-abyss-1000); }

/* ---- 스크린리더 전용 ---- */
.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

/* 본문 바로가기 — 탭하면 나타남 */
.skip-link {
  position: absolute;
  top: var(--s-3);
  left: var(--s-3);
  z-index: var(--z-modal);
  padding: var(--s-2) var(--s-4);
  background: var(--c-signal);
  color: var(--c-abyss-1000);
  font-weight: 600;
  border-radius: var(--r-card);
  transform: translateY(-200%);
  transition: transform var(--d-fast) var(--e-out);
}
.skip-link:focus-visible { transform: translateY(0); }

/* --------------------------------------------------------------------------
   레이아웃 프리미티브
   -------------------------------------------------------------------------- */

.shell {
  width: 100%;
  max-width: var(--w-content);
  margin-inline: auto;
  padding-inline: var(--s-gutter);
}

.section { position: relative; padding-block: var(--s-section); }

/* 섹션 사이 경계는 선 하나 — 밝은 그라데이션 블롭 대신 */
.section--ruled { border-top: 1px solid var(--c-line); }

.section__head {
  display: grid;
  gap: var(--s-4);
  margin-bottom: var(--s-7);
  max-width: 54rem;
}

/* 모든 섹션 라벨: 모노 + 자간 넓힘 + 신호 점 */
.eyebrow {
  display: inline-flex;
  align-items: center;
  gap: var(--s-3);
  font-family: var(--font-mono);
  font-size: var(--t-mono-xs);
  letter-spacing: var(--ls-label);
  text-transform: uppercase;
  color: var(--c-signal);
}
.eyebrow::before {
  content: '';
  width: 6px; height: 6px;
  border-radius: var(--r-pill);
  background: currentColor;
  box-shadow: 0 0 10px 2px var(--c-glow);
}

.section__title {
  font-size: var(--t-3xl);
  line-height: var(--lh-tight);
  letter-spacing: var(--ls-tight);
  font-weight: 700;
  text-wrap: balance;
}

.section__lede {
  font-size: var(--t-lg);
  color: var(--c-text-muted);
  max-width: var(--w-prose);
  text-wrap: pretty;
}

/* 제목 안의 의도적 줄바꿈 — 좁은 화면에서는 자연 줄바꿈에 맡긴다 */
@media (max-width: 48rem) {
  .br-lg { display: none; }
}

/* 강조 텍스트 — 액센트는 의미 있는 곳에만 */
.hl { color: var(--c-signal); }
.hl-probe { color: var(--c-probe); }

/* --------------------------------------------------------------------------
   배경 질감 — 청사진 그리드 + 필름 그레인
   본문 뒤에 고정되어 '계측기 화면' 분위기를 만든다.
   -------------------------------------------------------------------------- */

.backdrop {
  position: fixed;
  inset: 0;
  z-index: var(--z-grid);
  pointer-events: none;
}

.backdrop__grid {
  position: absolute;
  inset: -2px;
  background-image:
    linear-gradient(to right, var(--c-line) 1px, transparent 1px),
    linear-gradient(to bottom, var(--c-line) 1px, transparent 1px);
  background-size: 64px 64px;
  mask-image: radial-gradient(ellipse 120% 80% at 50% 0%, #000 10%, transparent 78%);
  opacity: 0.7;
}

.backdrop__grain {
  position: absolute;
  inset: 0;
  opacity: 0.035;
  background-image: var(--grain-url);
  background-size: 180px 180px;
  mix-blend-mode: overlay;
}

.backdrop__halo {
  position: absolute;
  top: -18vh; left: 50%;
  width: min(120vw, 1400px);
  aspect-ratio: 2 / 1;
  translate: -50% 0;
  background: radial-gradient(
    ellipse at center,
    color-mix(in oklab, var(--c-signal-deep) 22%, transparent) 0%,
    color-mix(in oklab, var(--c-brand) 20%, transparent) 40%,
    transparent 72%
  );
}

/* --------------------------------------------------------------------------
   버튼
   -------------------------------------------------------------------------- */

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--s-2);
  padding: 0.8em 1.5em;
  font-size: var(--t-sm);
  font-weight: 600;
  letter-spacing: -0.01em;
  border: 1px solid transparent;
  border-radius: var(--r-pill);
  cursor: pointer;
  background: none;
  transition: transform var(--d-fast) var(--e-out),
              background-color var(--d-fast) var(--e-out),
              border-color var(--d-fast) var(--e-out),
              box-shadow var(--d-normal) var(--e-out),
              color var(--d-fast) var(--e-out);
}
.btn:hover { transform: translateY(-2px); }
.btn:active { transform: translateY(0); }

.btn--primary {
  background: var(--c-signal);
  color: var(--c-abyss-1000);
}
.btn--primary:hover { box-shadow: 0 10px 30px -8px var(--c-glow); }

.btn--ghost {
  border-color: var(--c-line-strong);
  color: var(--c-text);
}
.btn--ghost:hover {
  border-color: var(--c-signal);
  color: var(--c-signal);
  background: oklch(80% 0.145 196 / 0.07);
}

/* 화살표가 호버 때 전진 — 방향을 알려주는 모션 */
.btn__arrow { transition: transform var(--d-normal) var(--e-out); }
.btn:hover .btn__arrow { transform: translateX(4px); }

/* --------------------------------------------------------------------------
   헤더 / 네비게이션
   -------------------------------------------------------------------------- */

.site-header {
  position: fixed;
  top: 0; left: 0; right: 0;
  z-index: var(--z-nav);
  transition: background-color var(--d-normal) var(--e-out),
              border-color var(--d-normal) var(--e-out),
              backdrop-filter var(--d-normal) var(--e-out);
  border-bottom: 1px solid transparent;
}

/* 스크롤되면 유리면으로 전환 */
.site-header.is-stuck {
  background: oklch(10% 0.028 258 / 0.78);
  backdrop-filter: blur(14px) saturate(1.3);
  border-bottom-color: var(--c-line);
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--s-5);
  height: 4.5rem;
}

/* ---- 워드마크: 실제 로고 (다크 배경용 변형) ---- */
.wordmark { display: inline-flex; align-items: center; }

/* width/height 속성으로 종횡비를 고정해 로드 중 레이아웃 이동을 막는다 */
.wordmark__logo {
  height: 2rem;
  width: auto;
  transition: opacity var(--d-fast) var(--e-out);
}
.wordmark:hover .wordmark__logo { opacity: 0.8; }

.site-footer__brand .wordmark__logo { height: 2.25rem; }

@media (max-width: 30rem) {
  .wordmark__logo { height: 1.75rem; }
}

.nav { display: flex; align-items: center; gap: var(--s-5); }
.nav__list { display: flex; align-items: center; gap: var(--s-5); }

.nav__link {
  position: relative;
  font-size: var(--t-sm);
  color: var(--c-text-muted);
  padding-block: var(--s-2);
  transition: color var(--d-fast) var(--e-out);
}
.nav__link::after {
  content: '';
  position: absolute;
  left: 0; bottom: 0;
  width: 100%; height: 1px;
  background: var(--c-signal);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--d-normal) var(--e-out);
}
.nav__link:hover,
.nav__link[aria-current='true'] { color: var(--c-text); }
.nav__link:hover::after,
.nav__link[aria-current='true']::after { transform: scaleX(1); }

/* 모바일 토글 — 데스크톱에서는 숨김 */
.nav-toggle {
  display: none;
  width: 2.75rem; height: 2.75rem;
  align-items: center;
  justify-content: center;
  border: 1px solid var(--c-line-strong);
  border-radius: var(--r-card);
  cursor: pointer;
}
.nav-toggle__bar {
  display: block;
  width: 18px; height: 1.5px;
  background: var(--c-text);
  position: relative;
  transition: background-color var(--d-fast) var(--e-out);
}
.nav-toggle__bar::before,
.nav-toggle__bar::after {
  content: '';
  position: absolute;
  left: 0;
  width: 100%; height: 100%;
  background: var(--c-text);
  transition: transform var(--d-normal) var(--e-out);
}
.nav-toggle__bar::before { transform: translateY(-5px); }
.nav-toggle__bar::after  { transform: translateY(5px); }

.nav-toggle[aria-expanded='true'] .nav-toggle__bar { background: transparent; }
.nav-toggle[aria-expanded='true'] .nav-toggle__bar::before { transform: rotate(45deg); }
.nav-toggle[aria-expanded='true'] .nav-toggle__bar::after  { transform: rotate(-45deg); }

/* 네비 항목 6개 기준으로 여유가 생기는 지점에서 햄버거로 전환 */
@media (max-width: 66rem) {
  .nav-toggle { display: inline-flex; }

  .nav {
    position: fixed;
    inset: 4.5rem 0 auto 0;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: var(--s-4) var(--s-gutter) var(--s-6);
    background: oklch(10% 0.028 258 / 0.97);
    backdrop-filter: blur(18px);
    border-bottom: 1px solid var(--c-line);
    /* 접힌 상태: 레이아웃 속성 대신 transform/opacity로만 애니메이션 */
    transform: translateY(-8px);
    opacity: 0;
    visibility: hidden;
    transition: transform var(--d-normal) var(--e-out),
                opacity var(--d-normal) var(--e-out),
                visibility var(--d-normal);
  }
  .nav.is-open { transform: translateY(0); opacity: 1; visibility: visible; }

  .nav__list { flex-direction: column; align-items: stretch; gap: 0; }
  .nav__link {
    padding: var(--s-4) 0;
    font-size: var(--t-lg);
    border-bottom: 1px solid var(--c-line);
  }
  .nav__link::after { display: none; }
  .nav .btn { margin-top: var(--s-5); justify-content: center; }
}

/* --------------------------------------------------------------------------
   푸터
   -------------------------------------------------------------------------- */

.site-footer {
  position: relative;
  z-index: var(--z-base);
  border-top: 1px solid var(--c-line);
  background: var(--c-abyss-1000);
  padding-block: var(--s-7) var(--s-5);
}

.site-footer__top {
  display: grid;
  grid-template-columns: minmax(0, 1.4fr) repeat(2, minmax(0, 1fr));
  gap: var(--s-6) var(--s-5);
  padding-bottom: var(--s-6);
}
@media (max-width: 48rem) {
  .site-footer__top { grid-template-columns: 1fr 1fr; }
  .site-footer__brand { grid-column: 1 / -1; }
}

.site-footer__brand p {
  margin-top: var(--s-3);
  color: var(--c-text-dim);
  font-size: var(--t-sm);
  max-width: 24rem;
}

.footer-col__title {
  font-family: var(--font-mono);
  font-size: var(--t-mono-xs);
  letter-spacing: var(--ls-label);
  text-transform: uppercase;
  color: var(--c-text-dim);
  margin-bottom: var(--s-3);
}
.footer-col li + li { margin-top: var(--s-2); }
.footer-col a,
.footer-col address {
  font-size: var(--t-sm);
  font-style: normal;
  color: var(--c-text-muted);
  transition: color var(--d-fast) var(--e-out);
}
.footer-col a:hover { color: var(--c-signal); }

/* 푸터 유튜브 링크 — 아이콘은 마스크로 올려 currentColor 를 따르게 한다 */
.footer-yt { display: inline-flex; align-items: center; gap: var(--s-2); }
.footer-yt__icon {
  width: 1.15rem; height: 1.15rem;
  flex: none;
  background: currentColor;
  -webkit-mask: url(../assets/youtube.svg) center / contain no-repeat;
          mask: url(../assets/youtube.svg) center / contain no-repeat;
}

.site-footer__bottom {
  display: flex;
  flex-wrap: wrap;
  gap: var(--s-3) var(--s-5);
  justify-content: space-between;
  align-items: center;
  padding-top: var(--s-5);
  border-top: 1px solid var(--c-line);
  font-family: var(--font-mono);
  font-size: var(--t-mono-xs);
  color: var(--c-text-dim);
}

/* --------------------------------------------------------------------------
   스크롤 진입 애니메이션 (JS가 .is-in 을 붙인다)
   -------------------------------------------------------------------------- */

.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity var(--d-slow) var(--e-out),
              transform var(--d-slow) var(--e-out);
  transition-delay: var(--reveal-delay, 0ms);
}
.reveal.is-in { opacity: 1; transform: none; }

/* JS 미동작 시 콘텐츠가 사라지지 않도록 */
.no-js .reveal { opacity: 1; transform: none; }

/* --------------------------------------------------------------------------
   모션 민감 사용자: 모든 비필수 모션 제거
   -------------------------------------------------------------------------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
  }
  .reveal { opacity: 1; transform: none; }
}