:root {
  --color-bg: #ffffff;
  --color-surface: #f8f9fc;
  --color-surface-alt: #f0f2f7;
  --color-text-primary: #1a1a2e;
  --color-text-secondary: #555770;
  --color-text-tertiary: #8b8da3;
  --color-border: #e2e4ed;
  --color-primary: #2563eb;
  --color-primary-light: #dbeafe;
  --color-primary-dark: #1d4ed8;
  --color-accent: #7c3aed;
  --color-accent-light: #ede9fe;
  --color-success: #16a34a;
  --color-warning: #d97706;
  --color-error: #dc2626;
  --color-on-primary: #fff;
  --color-header-bg: rgba(255, 255, 255, 0.85);
  --color-danger-light: #fee2e2;
  --color-warning-light: #fef3c7;
  --color-success-light: #dcfce7;
  --color-code-bg: #1e1e2e;
  --color-code-text: #cdd6f4;
  --color-reading-text: #92400e;
  --font-sans: "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, -apple-system, "Segoe UI", sans-serif;
  --font-display: system-ui, -apple-system, "Segoe UI", "PingFang SC", "Microsoft YaHei", sans-serif;
  --shadow-sm: 0 1px 2px rgba(26, 26, 46, 0.05);
  --shadow-md: 0 4px 12px rgba(26, 26, 46, 0.08);
  --shadow-lg: 0 8px 30px rgba(26, 26, 46, 0.1);
  --radius-sm: 8px;
  --radius-md: 12px;
  --radius-lg: 20px;
  --radius-full: 9999px;
  --transition: 200ms ease-out;
  --max-width: 72rem;
}

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
  overflow-x: hidden;
}

body {
  font-family: var(--font-sans);
  font-size: 1rem;
  line-height: 1.7;
  color: var(--color-text-primary);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
  -webkit-text-size-adjust: 100%;
}

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

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

a:hover {
  color: var(--color-primary-dark);
}

:focus-visible {
  outline: 3px solid var(--color-primary);
  outline-offset: 2px;
}

:focus:not(:focus-visible) {
  outline: none;
}

.container {
  width: 94%;
  margin-inline: auto;
}

.skip-link {
  position: absolute;
  top: -100%;
  left: 0;
  z-index: 1000;
  padding: 0.75rem 1.5rem;
  background: var(--color-primary);
  color: var(--color-on-primary);
  font-weight: 600;
  border-radius: 0 0 var(--radius-sm) 0;
}

.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;
}

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  padding: 0.75rem 1.75rem;
  font-size: 0.9375rem;
  font-weight: 600;
  border-radius: var(--radius-full);
  border: 2px solid transparent;
  cursor: pointer;
  transition: all var(--transition);
  min-height: 48px;
}

.btn-primary {
  background: var(--color-primary);
  color: var(--color-on-primary);
  border-color: var(--color-primary);
}

.btn-primary:hover {
  background: var(--color-primary-dark);
  border-color: var(--color-primary-dark);
  color: var(--color-on-primary);
  box-shadow: var(--shadow-md);
}

.btn-outline {
  background: transparent;
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.btn-outline:hover {
  background: var(--color-primary);
  color: var(--color-on-primary);
}

@media (min-width: 23.4375rem) {
  .container {
    width: min(90%, var(--max-width));
  }
}