/* === CSS Variables === */
:root {
  --color-bg: #f8f9fa;
  --color-surface: #ffffff;
  --color-text: #212529;
  --color-text-secondary: #6c757d;
  --color-primary: #0d6efd;
  --color-primary-rgb: 13, 110, 253;
  --color-primary-hover: #0b5ed7;
  --color-border: #dee2e6;
  --color-success: #198754;
  --color-error: #dc3545;
  --color-ad-bg: #f1f3f5;
  --shadow-card: 0 1px 3px rgba(0,0,0,0.08);
  --shadow-card-hover: 0 4px 12px rgba(0,0,0,0.12);
  --radius: 8px;
  --max-width: 960px;
  --font-mono: 'Consolas', 'Monaco', 'Courier New', monospace;
}

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

html { font-size: 16px; scroll-behavior: smooth; }

body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, sans-serif;
  color: var(--color-text);
  background: var(--color-bg);
  line-height: 1.6;
  min-height: 100vh;
}

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

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

/* === Navigation === */
.nav {
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky; top: 0; z-index: 100;
}
.nav-inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 16px;
  display: flex;
  align-items: center;
  height: 56px;
  gap: 24px;
}
.nav-logo {
  font-size: 1.25rem;
  font-weight: 700;
  color: var(--color-text);
  white-space: nowrap;
}
.nav-logo:hover { text-decoration: none; color: var(--color-primary); }
.nav-links {
  display: flex; gap: 4px;
  overflow-x: auto;
  scrollbar-width: none;
}
.nav-links::-webkit-scrollbar { display: none; }
.nav-links a {
  color: var(--color-text-secondary);
  padding: 6px 12px;
  border-radius: 6px;
  font-size: 0.875rem;
  white-space: nowrap;
}
.nav-links a:hover,
.nav-links a.active {
  color: var(--color-primary);
  background: #e7f1ff;
  text-decoration: none;
}

/* === Layout === */
.main {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 32px 16px 48px;
}

/* === Cards === */
.card-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
  gap: 20px;
  margin: 32px 0;
}
.card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow-card);
  transition: box-shadow 0.2s, transform 0.2s;
}
.card:hover {
  box-shadow: var(--shadow-card-hover);
  transform: translateY(-2px);
}
.card h2 { font-size: 1.125rem; margin-bottom: 8px; }
.card h2 a { color: var(--color-text); }
.card h2 a:hover { color: var(--color-primary); text-decoration: none; }
.card p { color: var(--color-text-secondary); font-size: 0.875rem; }

/* === Hero (homepage) === */
.hero { text-align: center; padding: 48px 16px 24px; }
.hero h1 { font-size: 2rem; margin-bottom: 8px; }
.hero p { color: var(--color-text-secondary); font-size: 1.125rem; }

/* === Tool Page === */
.tool-header { margin-bottom: 24px; }
.breadcrumb {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  margin-bottom: 12px;
}
.breadcrumb a { color: var(--color-text-secondary); }
.tool-header h1 { font-size: 1.5rem; }

/* === Tool Area === */
.tool-area {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius);
  padding: 24px;
  margin-bottom: 24px;
}
.tool-area textarea,
.tool-area input[type="text"],
.tool-area input[type="url"] {
  width: 100%;
  padding: 12px;
  border: 1px solid var(--color-border);
  border-radius: 6px;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  resize: vertical;
  min-height: 200px;
}
.tool-area textarea:focus,
.tool-area input:focus {
  outline: none;
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(var(--color-primary-rgb), 0.15);
}

/* === Buttons === */
.btn-group { display: flex; flex-wrap: wrap; gap: 8px; margin: 12px 0; }
.btn {
  padding: 8px 20px;
  border: 1px solid var(--color-border);
  border-radius: 6px;
  background: var(--color-surface);
  color: var(--color-text);
  font-size: 0.875rem;
  cursor: pointer;
  transition: background 0.15s, border-color 0.15s;
}
.btn:hover { background: #e9ecef; }
.btn-primary {
  background: var(--color-primary);
  color: #fff;
  border-color: var(--color-primary);
}
.btn-primary:hover { background: var(--color-primary-hover); }

/* === Output Area === */
.output-area {
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: 6px;
  padding: 16px;
  font-family: var(--font-mono);
  font-size: 0.875rem;
  min-height: 200px;
  white-space: pre-wrap;
  word-break: break-all;
  max-height: 500px;
  overflow-y: auto;
}
.output-area.success { border-left: 3px solid var(--color-success); }
.output-area.error { border-left: 3px solid var(--color-error); color: var(--color-error); }

/* === Status === */
.status-bar {
  display: flex; align-items: center; gap: 16px;
  padding: 8px 0; font-size: 0.8125rem;
  color: var(--color-text-secondary);
}

/* === Slider === */
input[type="range"] {
  width: 100%;
  accent-color: var(--color-primary);
}

/* === AdSense === */
.ad-slot {
  background: var(--color-ad-bg);
  border: 1px dashed var(--color-border);
  border-radius: var(--radius);
  min-height: 90px;
  display: flex;
  align-items: center;
  justify-content: center;
  margin: 24px 0;
  text-align: center;
}
.ad-slot .ad-label {
  font-size: 0.75rem;
  color: #adb5bd;
  text-transform: uppercase;
  letter-spacing: 0.05em;
}
.ad-slot-banner { min-height: 90px; }
.ad-slot-content { min-height: 250px; }

/* === Related Tools === */
.related-tools { margin-top: 32px; padding-top: 24px; border-top: 1px solid var(--color-border); }
.related-tools h3 { font-size: 1rem; margin-bottom: 12px; }
.related-tools .related-links { display: flex; flex-wrap: wrap; gap: 8px; }
.related-tools a {
  padding: 6px 14px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 20px;
  font-size: 0.8125rem;
  color: var(--color-text);
}
.related-tools a:hover { border-color: var(--color-primary); color: var(--color-primary); text-decoration: none; }

/* === Footer === */
.footer {
  text-align: center;
  padding: 32px 16px;
  color: var(--color-text-secondary);
  font-size: 0.8125rem;
  border-top: 1px solid var(--color-border);
}
.footer a { color: var(--color-text-secondary); }
.footer a:hover { color: var(--color-primary); }

/* === Featured Tools === */
.featured-tools { margin-top: 40px; padding-top: 24px; border-top: 1px solid var(--color-border); }
.featured-tools h2 { font-size: 1.125rem; margin-bottom: 16px; }
.featured-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(140px, 1fr));
  gap: 10px;
}
.featured-item {
  display: block;
  padding: 10px 14px;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: 8px;
  font-size: 0.875rem;
  color: var(--color-text);
  text-align: center;
  transition: border-color 0.2s, color 0.2s;
}
.featured-item:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
  text-decoration: none;
}

/* === Responsive === */
@media (max-width: 640px) {
  .hero h1 { font-size: 1.5rem; }
  .card-grid { grid-template-columns: 1fr; }
  .nav-links { gap: 0; }
  .nav-links a { padding: 4px 8px; font-size: 0.75rem; }
  .tool-area { padding: 16px; }
}