/* =========================================================
   CSS Development Lab 01
   Responsive Header + Multi-level Navigation
   ========================================================= */

/* ---------- 1. Base ---------- */
:root {
  --page-max: 1200px;
  --header-h: 76px;
  --text: #171717;
  --muted: #676767;
  --line: #e8e8e8;
  --surface: #ffffff;
  --soft: #f6f6f3;
  --accent: #171717;
  --radius: 20px;
  --shadow: 0 18px 45px rgba(0, 0, 0, 0.08);
  --ease: 220ms ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  color: var(--text);
  background: var(--surface);
  font-family: Inter, "PingFang SC", "Microsoft YaHei", system-ui, -apple-system, sans-serif;
  line-height: 1.6;
}

body.nav-open {
  overflow: hidden;
}

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

button,
a {
  -webkit-tap-highlight-color: transparent;
}

button {
  font: inherit;
}

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

/* ---------- 2. Header ---------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--header-h);
  background: rgba(255, 255, 255, 0.92);
  border-bottom: 1px solid rgba(0, 0, 0, 0.06);
  backdrop-filter: blur(16px);
}

.nav-wrap {
  width: min(calc(100% - 40px), var(--page-max));
  height: 100%;
  margin-inline: auto;
  display: flex;
  align-items: center;
  gap: 28px;
}

.brand {
  flex: 0 0 auto;
  display: inline-flex;
  align-items: center;
  gap: 10px;
  font-weight: 800;
  letter-spacing: -0.02em;
}

.brand-mark {
  width: 34px;
  aspect-ratio: 1;
  display: grid;
  place-items: center;
  border-radius: 10px;
  color: #fff;
  background: #171717;
}

.brand-text {
  font-size: 1rem;
}

.desktop-nav {
  margin-inline: auto;
}

.menu,
.submenu,
.mobile-menu,
.mobile-submenu-list {
  margin: 0;
  padding: 0;
  list-style: none;
}

.menu {
  display: flex;
  align-items: center;
  gap: 4px;
}

.menu > li {
  position: relative;
}

.menu > li > a {
  min-height: 44px;
  padding: 0 14px;
  display: flex;
  align-items: center;
  gap: 6px;
  border-radius: 10px;
  font-size: 0.95rem;
  font-weight: 600;
  transition: background var(--ease), color var(--ease);
}

.menu > li > a:hover,
.menu > li > a:focus-visible {
  background: var(--soft);
}

.menu-arrow {
  width: 14px;
  height: 14px;
  transition: transform var(--ease);
}

.has-submenu:hover > a .menu-arrow,
.has-submenu:focus-within > a .menu-arrow {
  transform: rotate(180deg);
}

/* ---------- 3. Desktop submenu ---------- */
.submenu {
  position: absolute;
  top: calc(100% + 10px);
  left: 0;
  min-width: 210px;
  padding: 8px;
  background: var(--surface);
  border: 1px solid var(--line);
  border-radius: 14px;
  box-shadow: var(--shadow);

  opacity: 0;
  visibility: hidden;
  transform: translateY(8px);
  transition:
    opacity var(--ease),
    visibility var(--ease),
    transform var(--ease);
}

.submenu::before {
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  top: -12px;
  height: 12px;
}

.has-submenu:hover > .submenu,
.has-submenu:focus-within > .submenu {
  opacity: 1;
  visibility: visible;
  transform: translateY(0);
}

.submenu a {
  display: block;
  padding: 10px 12px;
  border-radius: 9px;
  color: #333;
  font-size: 0.92rem;
  transition: background var(--ease), transform var(--ease);
}

.submenu a:hover,
.submenu a:focus-visible {
  background: var(--soft);
  transform: translateX(2px);
}

.header-cta,
.drawer-cta,
.primary-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-height: 44px;
  padding: 0 18px;
  border-radius: 999px;
  color: #fff;
  background: var(--accent);
  font-size: 0.92rem;
  font-weight: 700;
  transition: transform var(--ease), opacity var(--ease);
}

.header-cta:hover,
.drawer-cta:hover,
.primary-btn:hover {
  transform: translateY(-1px);
  opacity: 0.9;
}

.menu-toggle {
  display: none;
  width: 44px;
  height: 44px;
  padding: 10px;
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--surface);
  cursor: pointer;
}

/* ---------- 4. Mobile drawer ---------- */
.drawer-backdrop {
  position: fixed;
  inset: 0;
  z-index: 190;
  background: rgba(0, 0, 0, 0.42);
  opacity: 0;
  transition: opacity 260ms ease;
}

.drawer-backdrop.is-visible {
  opacity: 1;
}

.mobile-drawer {
  position: fixed;
  top: 0;
  right: 0;
  z-index: 200;
  width: min(88vw, 390px);
  height: 100dvh;
  display: flex;
  flex-direction: column;
  background: var(--surface);
  box-shadow: -24px 0 60px rgba(0, 0, 0, 0.16);
  transform: translateX(100%);
  visibility: hidden;
  transition:
    transform 300ms cubic-bezier(.2, .8, .2, 1),
    visibility 300ms;
}

.mobile-drawer.is-open {
  transform: translateX(0);
  visibility: visible;
}

.drawer-head {
  min-height: var(--header-h);
  padding-inline: 20px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  border-bottom: 1px solid var(--line);
}

.drawer-close {
  width: 44px;
  height: 44px;
  padding: 10px;
  border: 0;
  border-radius: 12px;
  background: var(--soft);
  cursor: pointer;
}

.mobile-nav {
  flex: 1;
  padding: 18px 20px 28px;
  overflow-y: auto;
}

.mobile-menu > li {
  border-bottom: 1px solid var(--line);
}

.mobile-menu > li > a,
.mobile-row > a {
  min-height: 56px;
  display: flex;
  align-items: center;
  font-weight: 700;
}

.mobile-row {
  display: flex;
  align-items: center;
}

.mobile-row > a {
  flex: 1;
}

.submenu-toggle {
  flex: 0 0 44px;
  width: 44px;
  height: 44px;
  padding: 10px;
  display: grid;
  place-items: center;
  border: 0;
  border-radius: 10px;
  background: transparent;
  cursor: pointer;
}

.submenu-toggle img {
  width: 20px;
  height: 20px;
  transition: transform var(--ease);
}

.has-children.is-open .submenu-toggle img {
  transform: rotate(180deg);
}

.mobile-submenu {
  display: grid;
  grid-template-rows: 0fr;
  transition: grid-template-rows 260ms ease;
}

.mobile-submenu-list {
  min-height: 0;
  overflow: hidden;
}

.has-children.is-open > .mobile-submenu {
  grid-template-rows: 1fr;
}

.mobile-submenu a {
  display: block;
  padding: 0 14px 12px;
  color: var(--muted);
  font-size: 0.94rem;
}

.drawer-cta {
  width: 100%;
  margin-top: 24px;
}

/* ---------- 5. Demo page ---------- */
.hero {
  min-height: calc(100vh - var(--header-h));
  display: grid;
  place-items: center;
  padding: clamp(72px, 10vw, 140px) 20px;
  background:
    radial-gradient(circle at 80% 15%, rgba(0,0,0,.06), transparent 28%),
    linear-gradient(180deg, #fafaf8 0%, #f2f2ef 100%);
}

.hero-inner {
  width: min(100%, 920px);
  text-align: center;
}

.eyebrow {
  margin: 0 0 14px;
  color: #787878;
  font-size: 0.78rem;
  font-weight: 800;
  letter-spacing: 0.16em;
}

.hero h1,
.section-head h2,
.content-section h2,
.contact h2 {
  margin: 0;
  letter-spacing: -0.04em;
  line-height: 1.04;
}

.hero h1 {
  font-size: clamp(2.7rem, 7vw, 6.4rem);
}

.hero-text {
  max-width: 720px;
  margin: 26px auto 30px;
  color: var(--muted);
  font-size: clamp(1rem, 2vw, 1.2rem);
}

.features {
  padding: clamp(80px, 10vw, 130px) 20px;
}

.section-head,
.feature-grid,
.content-section,
.contact {
  width: min(100%, var(--page-max));
  margin-inline: auto;
}

.section-head h2,
.content-section h2,
.contact h2 {
  font-size: clamp(2rem, 4vw, 4rem);
}

.feature-grid {
  margin-top: 44px;
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 18px;
}

.feature-card {
  min-height: 240px;
  padding: 28px;
  display: flex;
  flex-direction: column;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
}

.feature-card span {
  color: #999;
  font-size: 0.8rem;
  font-weight: 800;
}

.feature-card h3 {
  margin: auto 0 10px;
  font-size: 1.25rem;
}

.feature-card p {
  margin: 0;
  color: var(--muted);
}

.content-section {
  min-height: 72vh;
  padding: clamp(72px, 10vw, 130px) 0;
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(280px, .8fr);
  align-items: center;
  gap: clamp(40px, 8vw, 120px);
}

.content-section > p {
  margin: 0;
  color: var(--muted);
  font-size: 1.08rem;
}

.content-section.alt {
  padding-inline: clamp(24px, 5vw, 72px);
  border-radius: 30px;
  background: var(--soft);
}

.contact {
  padding: 120px 20px 160px;
  text-align: center;
}

/* ---------- 6. Responsive ---------- */
@media (max-width: 900px) {
  .desktop-nav,
  .header-cta {
    display: none;
  }

  .nav-wrap {
    width: min(calc(100% - 32px), var(--page-max));
    justify-content: space-between;
  }

  .menu-toggle {
    display: block;
  }

  .feature-grid {
    grid-template-columns: repeat(2, 1fr);
  }

  .content-section {
    width: min(calc(100% - 40px), var(--page-max));
  }
}

@media (max-width: 640px) {
  :root {
    --header-h: 68px;
  }

  .nav-wrap {
    width: calc(100% - 24px);
  }

  .brand-text {
    font-size: 0.95rem;
  }

  .hero {
    min-height: calc(88vh - var(--header-h));
    padding-inline: 18px;
  }

  .hero h1 {
    font-size: clamp(2.6rem, 14vw, 4.5rem);
  }

  .feature-grid {
    grid-template-columns: 1fr;
  }

  .feature-card {
    min-height: 200px;
  }

  .content-section,
  .content-section.alt {
    width: calc(100% - 28px);
    min-height: auto;
    padding: 80px 20px;
    grid-template-columns: 1fr;
    gap: 26px;
  }

  .contact {
    padding: 100px 20px 120px;
  }
}

/* ---------- 7. Accessibility ---------- */
:focus-visible {
  outline: 2px solid #171717;
  outline-offset: 3px;
}

@media (prefers-reduced-motion: reduce) {
  *,
  *::before,
  *::after {
    scroll-behavior: auto !important;
    transition-duration: 0.01ms !important;
    animation-duration: 0.01ms !important;
  }
}