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

/* === Variables === */
:root {
  --color-primary: #2563eb;
  --color-primary-hover: #1d4ed8;
  --color-bg: #f8fafc;
  --color-surface: #ffffff;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-border: #e2e8f0;
  --color-success: #22c55e;
  --color-error: #ef4444;
  --color-warning: #f59e0b;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0, 0, 0, 0.1);
  --max-width: 1200px;
}

/* === Base === */
body {
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

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

a:hover {
  text-decoration: underline;
}

/* === Header === */
.site-header {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  padding: 12px 0;
  position: sticky;
  top: 0;
  z-index: 100;
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
}

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

.site-header .logo span {
  color: var(--color-primary);
}

.site-header nav a {
  color: var(--color-text-secondary);
  margin-left: 24px;
  font-size: 0.9rem;
}

.site-header nav a:hover {
  color: var(--color-primary);
  text-decoration: none;
}

/* === Container === */
.container {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 20px;
  width: 100%;
}

/* === Footer === */
.site-footer {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: 24px 0;
  margin-top: auto;
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 0.85rem;
}

.site-footer .related-tools {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 16px;
  margin-bottom: 16px;
}

.site-footer .related-tools a {
  color: var(--color-text-secondary);
  font-size: 0.85rem;
}

.site-footer .copyright {
  color: var(--color-text-secondary);
}

/* === Ad Slots === */
.ad-sidebar {
  min-width: 300px;
  max-width: 300px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 16px;
  text-align: center;
  align-self: flex-start;
  position: sticky;
  top: 80px;
}

.ad-bottom {
  background: var(--color-surface);
  border-top: 1px solid var(--color-border);
  padding: 20px 0;
  text-align: center;
  margin-top: 40px;
}

.ad-label {
  font-size: 0.75rem;
  color: var(--color-text-secondary);
  margin-bottom: 8px;
}

/* === Responsive === */
@media (max-width: 768px) {
  .ad-sidebar {
    display: none;
  }

  .site-header .container {
    flex-direction: column;
    gap: 8px;
  }

  .site-header nav a {
    margin-left: 12px;
    margin-right: 12px;
  }
}