/* =====================================================
   上海铂米瑞光电技术有限公司 — 基础样式
   ===================================================== */

/* CSS 变量 */
:root {
  --bg-page: #0f0f0f;
  --bg-header: #FFFFFF;
  --text-header: #1A1A1A;
  --text-primary: #1A1A1A;
  --text-secondary: #4A6572;
  --text-muted: #7A8B94;
  --table-header-bg: #5D7A8C;
  --table-header-text: #FFFFFF;
  --table-cell-bg: #F4F6F7;
  --table-cell-bg-alt: #EAEFF1;
  --table-cell-text: #4A6572;
  --accent: #2C4A5E;
  --accent-light: #3D5F73;
  --border-color: #E2E8EC;
  --hero-overlay: rgba(255, 255, 255, 0.55);
  --font-family: "PingFang SC", "Microsoft YaHei", "Helvetica Neue", Arial, sans-serif;
  --font-weight-light: 300;
  --font-weight-regular: 400;
  --font-weight-medium: 500;
  --letter-spacing-wide: 0.08em;
  --letter-spacing-wider: 0.12em;
  --container-max: 1200px;
  --container-narrow: 960px;
  --space-unit: 8px;
  --space-xs: 8px;
  --space-sm: 16px;
  --space-md: 24px;
  --space-lg: 40px;
  --space-xl: 64px;
  --space-2xl: 96px;
  --radius-sm: 4px;
  --radius-md: 8px;
  --transition: 0.25s ease;
}

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

html {
  scroll-behavior: smooth;
}

body {
  margin: 0;
  padding: 0;
  font-family: var(--font-family);
  font-weight: var(--font-weight-light);
  font-size: 16px;
  line-height: 1.7;
  color: var(--text-primary);
  background-color: var(--bg-page);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

html[lang="en"] body {
  line-height: 1.6;
}

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

a {
  color: var(--accent);
  text-decoration: none;
  transition: color var(--transition);
}

a:hover, a:focus {
  color: var(--accent-light);
  text-decoration: underline;
}

h1, h2, h3, h4, h5, h6 {
  margin: 0 0 var(--space-md) 0;
  font-weight: var(--font-weight-medium);
  line-height: 1.3;
  color: var(--text-primary);
  letter-spacing: 0.02em;
}

h1 { font-size: clamp(2rem, 5vw, 3rem); }
h2 { font-size: clamp(1.5rem, 3vw, 2rem); }
h3 { font-size: 1.25rem; }
h4 { font-size: 1.1rem; }

p {
  margin: 0 0 var(--space-md) 0;
  color: var(--text-secondary);
}

ul, ol {
  margin: 0 0 var(--space-md) 0;
  padding-left: 1.5em;
  color: var(--text-secondary);
}

/* 工具类 */
.container {
  width: 100%;
  max-width: var(--container-max);
  margin: 0 auto;
  padding: 0 var(--space-md);
}

.container--narrow {
  max-width: var(--container-narrow);
}

.section {
  padding: var(--space-2xl) 0;
}

.section-title {
  text-align: center;
  margin-bottom: var(--space-xl);
}

.section-title h2 {
  margin-bottom: var(--space-sm);
  letter-spacing: var(--letter-spacing-wide);
}

.section-title p {
  max-width: 640px;
  margin: 0 auto;
  color: var(--text-muted);
  font-size: 0.95rem;
  letter-spacing: 0.03em;
}

.lead {
  font-size: 1.15rem;
  color: var(--text-secondary);
  letter-spacing: 0.03em;
}

.skip-link {
  position: absolute;
  top: -40px;
  left: 0;
  background: var(--bg-header);
  color: var(--text-header);
  padding: 8px 16px;
  z-index: 100;
  transition: top var(--transition);
}

.skip-link:focus {
  top: 0;
}

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}