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

:root {
  --color-bg: #fff;
  --color-text: #1a1a2e;
  --color-muted: #6b7280;
  --color-accent: #2563eb;
  --color-border: #e5e7eb;
  --color-surface: #f9fafb;
  --font-sans: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  --max-width: 720px;
  --gutter: 1.5rem;
}

html {
  font-family: var(--font-sans);
  font-size: 18px;
  line-height: 1.6;
  color: var(--color-text);
  background: var(--color-bg);
  -webkit-font-smoothing: antialiased;
}

body {
  min-height: 100vh;
}

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

a:hover {
  text-decoration: underline;
}

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

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-bg);
  border-bottom: 1px solid var(--color-border);
}

.header-inner {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0.75rem var(--gutter);
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.logo {
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--color-text);
}

.logo:hover {
  text-decoration: none;
}

nav {
  display: flex;
  align-items: center;
  gap: 1.5rem;
}

nav a {
  color: var(--color-muted);
  font-size: 0.9rem;
}

nav a:hover {
  color: var(--color-text);
  text-decoration: none;
}

.search-form {
  display: flex;
}

.search-form input {
  padding: 0.5rem 1rem;
  border: 1px solid var(--color-border);
  border-radius: 9999px;
  font-size: 0.875rem;
  width: 200px;
  outline: none;
  transition: border-color 0.2s, width 0.2s;
}

.search-form input:focus {
  border-color: var(--color-accent);
  width: 280px;
}

.site-footer {
  margin-top: 4rem;
  padding: 2rem var(--gutter);
  border-top: 1px solid var(--color-border);
  text-align: center;
  color: var(--color-muted);
  font-size: 0.875rem;
}

@media (max-width: 640px) {
  :root {
    --gutter: 1rem;
  }
  html {
    font-size: 16px;
  }
  .search-form input {
    width: 140px;
  }
  .search-form input:focus {
    width: 180px;
  }
}