/* =========================================
   1. Design System Variables (Per design.md)
   ========================================= */
:root {
  --pure-black: #000000;
  --light-gray: #f5f5f7;
  --near-black: #1d1d1f;
  --apple-blue: #0071e3;
  --link-light: #0066cc;
  --link-dark: #2997ff;
  --focus-ring: #0071e3;
  --text-white: #ffffff;
  --text-black-80: rgba(0, 0, 0, 0.8);
  --text-white-80: rgba(255, 255, 255, 0.8);
  --dark-surface: #1d1d1f;
  --card-shadow: rgba(0, 0, 0, 0.12) 3px 5px 30px 0px;
}

/* =========================================
   2. Global Reset & Typography
   ========================================= */
* { box-sizing: border-box; }
body {
  margin: 0; padding: 0;
  background-color: var(--light-gray);
  font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Text', 'Helvetica Neue', sans-serif;
  -webkit-font-smoothing: antialiased;
  padding-top: 48px;
  color: var(--near-black);
}

.sf-display { font-family: -apple-system, BlinkMacSystemFont, 'SF Pro Display', sans-serif; }

/* 响应式字体 & 负字母间距 (Strictly per design.md) */
h1, .display-hero {
  font-size: clamp(40px, 8vw, 56px);
  font-weight: 600;
  line-height: 1.07;
  letter-spacing: -0.28px;
}

h2.section-heading {
  font-size: clamp(32px, 6vw, 40px);
  font-weight: 600;
  line-height: 1.1;
  letter-spacing: -0.2px;
}

p, .body-text {
  font-size: 17px;
  line-height: 1.47;
  letter-spacing: -0.374px;
}

.caption {
  font-size: 14px;
  font-weight: 600;
  line-height: 1.29;
  letter-spacing: -0.224px;
}

/* =========================================
   3. Responsive Navigation (Glass Effect)
   ========================================= */
.apple-nav {
  position: fixed; top: 0; left: 0; right: 0; height: 48px;
  background: rgba(0, 0, 0, 0.8);
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  z-index: 9999; display: flex; justify-content: center;
}

.nav-links {
  display: flex; gap: clamp(15px, 4vw, 32px);
  list-style: none; margin: 0; padding: 0 20px;
  align-items: center;
}

.nav-links a {
  color: #fff; font-size: 12px; text-decoration: none;
  letter-spacing: -0.12px; transition: opacity 0.2s;
}

@media (max-width: 768px) {
  .nav-links { overflow-x: auto; white-space: nowrap; -webkit-overflow-scrolling: touch; justify-content: flex-start; }
  .nav-links::-webkit-scrollbar { display: none; }
}

/* =========================================
   4. Layout & Grid
   ========================================= */
.apple-section { padding: clamp(60px, 10vw, 100px) 20px; width: 100%; display: flex; flex-direction: column; align-items: center; }
.section-dark { background-color: var(--pure-black); color: #fff; }
.section-light { background-color: var(--light-gray); color: var(--near-black); }

.container { width: 100%; max-width: 980px; margin: 0 auto; }
.grid-2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(320px, 1fr)); gap: 24px; }
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(280px, 1fr)); gap: 24px; }

/* =========================================
   5. Components (Cards, Buttons, Photos)
   ========================================= */
.card { border-radius: 8px; padding: 32px; transition: transform 0.3s ease; }
.card-light { background: #fff; box-shadow: var(--card-shadow); }
.card-dark { background: var(--dark-surface); border: 1px solid rgba(255,255,255,0.1); }

.btn-primary {
  background: var(--apple-blue); color: #fff;
  padding: 12px 24px; border-radius: 980px;
  text-decoration: none; display: inline-flex; align-items: center; gap: 8px;
}

.photo-container { border-radius: 8px; overflow: hidden; box-shadow: var(--card-shadow); }
.photo-container img { width: 100%; height: auto; display: block; }

.apple-footer {
  background: var(--pure-black); color: var(--text-white-80);
  padding: 40px 20px; text-align: center; font-size: 12px;
}