/* ============================================
   KDSS Website — Base Styles
   CSS Reset + Custom Properties + Typography
   ============================================ */

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

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
  font-size: 16px;
}

body {
  font-family: var(--font-sans);
  background-color: var(--bg-primary);
  color: var(--text-primary);
  line-height: 1.7;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

a {
  color: var(--accent-blue);
  text-decoration: none;
  transition: color 0.2s ease;
}

a:hover {
  color: var(--accent-purple);
}

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

ul, ol {
  list-style: none;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
  color: inherit;
}

input, textarea, select {
  font-family: inherit;
  font-size: inherit;
  color: inherit;
}

table {
  border-collapse: collapse;
  width: 100%;
}

/* --- CSS Custom Properties --- */
:root {
  /* Backgrounds / 背景 — 明亮科技风（带微蓝底色） */
  --bg-primary: #fafbff;
  --bg-secondary: #f0f4ff;
  --bg-tertiary: #e6ecf9;

  /* Text / 文字 */
  --text-primary: #0f172a;
  --text-secondary: #3e4c63;
  --text-muted: #7c8ba5;

  /* Accent / 强调色（高饱和） */
  --accent-blue: #2563eb;
  --accent-purple: #7c3aed;
  --accent-cyan: #0891b2;
  --accent-green: #16a34a;

  /* Gradients / 渐变 */
  --gradient-hero: linear-gradient(135deg, #2563eb, #7c3aed);
  --gradient-card: linear-gradient(180deg, rgba(37,99,235,0.03), rgba(124,58,237,0.01));

  /* Borders / 边框 */
  --border-color: rgba(37, 99, 235, 0.1);
  --border-hover: rgba(37, 99, 235, 0.2);

  /* Fonts / 字体 */
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'PingFang SC', 'Microsoft YaHei', sans-serif;
  --font-mono: 'JetBrains Mono', 'Fira Code', 'Cascadia Code', monospace;

  /* Spacing / 间距 */
  --space-xs: 4px;
  --space-sm: 8px;
  --space-md: 16px;
  --space-lg: 24px;
  --space-xl: 32px;
  --space-2xl: 48px;
  --space-3xl: 64px;
  --space-4xl: 96px;

  /* Radius / 圆角 */
  --radius-sm: 6px;
  --radius-md: 8px;
  --radius-lg: 12px;
  --radius-xl: 16px;

  /* Shadows / 阴影（带蓝色调） */
  --shadow-sm: 0 1px 3px rgba(37,99,235,0.06), 0 1px 2px rgba(0,0,0,0.04);
  --shadow-md: 0 4px 16px rgba(37,99,235,0.1);
  --shadow-lg: 0 8px 32px rgba(37,99,235,0.12);

  /* Transitions / 过渡 */
  --transition-fast: 0.15s ease;
  --transition-base: 0.2s ease;
  --transition-slow: 0.3s ease;

  /* Layout / 布局 */
  --max-width: 1200px;
  --nav-height: 64px;
}

/* --- Typography --- */
h1, h2, h3, h4, h5, h6 {
  font-weight: 700;
  line-height: 1.3;
  color: var(--text-primary);
}

h1 { font-size: 48px; letter-spacing: -0.02em; }
h2 { font-size: 36px; letter-spacing: -0.01em; }
h3 { font-size: 28px; }
h4 { font-size: 24px; }
h5 { font-size: 20px; }
h6 { font-size: 18px; }

p {
  color: var(--text-secondary);
  line-height: 1.7;
}

code, pre {
  font-family: var(--font-mono);
}

code {
  font-size: 0.875em;
  background: var(--bg-tertiary);
  padding: 2px 6px;
  border-radius: var(--radius-sm);
  color: var(--accent-cyan);
}

pre {
  background: var(--bg-secondary);
  border: 1px solid var(--border-color);
  border-radius: var(--radius-md);
  padding: var(--space-lg);
  overflow-x: auto;
  font-size: 14px;
  line-height: 1.6;
}

pre code {
  background: none;
  padding: 0;
  font-size: inherit;
  color: var(--text-primary);
}

/* --- Utility --- */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-lg);
}

.section {
  padding: var(--space-4xl) 0;
}

.section-header {
  text-align: center;
  margin-bottom: var(--space-3xl);
}

.section-header h2 {
  margin-bottom: var(--space-md);
}

.section-header p {
  font-size: 18px;
  max-width: 640px;
  margin: 0 auto;
}

.text-gradient {
  background: var(--gradient-hero);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.text-center { text-align: center; }
.text-left { text-align: left; }
.text-right { text-align: right; }

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

/* --- Selection --- */
::selection {
  background: rgba(37, 99, 235, 0.15);
  color: var(--text-primary);
}

/* --- Scrollbar --- */
::-webkit-scrollbar {
  width: 8px;
  height: 8px;
}

::-webkit-scrollbar-track {
  background: var(--bg-primary);
}

::-webkit-scrollbar-thumb {
  background: var(--bg-tertiary);
  border-radius: 4px;
}

::-webkit-scrollbar-thumb:hover {
  background: var(--text-muted);
}

/* --- Responsive Typography --- */
@media (max-width: 768px) {
  h1 { font-size: 32px; }
  h2 { font-size: 28px; }
  h3 { font-size: 22px; }
  h4 { font-size: 20px; }

  .section {
    padding: var(--space-3xl) 0;
  }

  .section-header {
    margin-bottom: var(--space-2xl);
  }
}