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

:root {
  --bg: #f5f7fa;
  --surface: #ffffff;
  --text: #1a1a2e;
  --text-muted: #6b7280;
  --primary: #2563eb;
  --primary-hover: #1d4ed8;
  --border: #e5e7eb;
  --sidebar-bg: #1a1a2e;
  --sidebar-text: #cbd5e1;
  --sidebar-active: #2563eb;
  --radius: 8px;
  --shadow: 0 1px 3px rgba(0,0,0,0.08);
  --sidebar-w: 260px;
}

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

/* Sidebar */
.sidebar {
  position: fixed;
  top: 0; left: 0;
  width: var(--sidebar-w);
  height: 100vh;
  background: var(--sidebar-bg);
  color: var(--sidebar-text);
  overflow-y: auto;
  display: flex;
  flex-direction: column;
  z-index: 100;
  transition: transform 0.3s;
}
.logo {
  display: block;
  padding: 20px 20px 16px;
  font-size: 1.3rem;
  font-weight: 700;
  color: #fff;
  text-decoration: none;
  border-bottom: 1px solid rgba(255,255,255,0.08);
}
.nav-list { list-style: none; padding: 12px 0; flex: 1; }
.nav-category {
  padding: 16px 20px 6px;
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 1.5px;
  color: rgba(255,255,255,0.35);
  font-weight: 600;
}
.nav-link {
  display: flex;
  align-items: center;
  gap: 10px;
  padding: 8px 20px;
  color: var(--sidebar-text);
  text-decoration: none;
  font-size: 0.88rem;
  border-left: 3px solid transparent;
  transition: background 0.15s, border-color 0.15s;
}
.nav-link:hover { background: rgba(255,255,255,0.06); }
.nav-link.active {
  background: rgba(37,99,235,0.15);
  border-left-color: var(--primary);
  color: #fff;
}
.nav-icon {
  width: 28px;
  text-align: center;
  font-size: 0.8rem;
  font-weight: 700;
  flex-shrink: 0;
}
.nav-footer {
  padding: 16px 20px;
  border-top: 1px solid rgba(255,255,255,0.08);
}
.nav-footer a { color: var(--sidebar-text); font-size: 0.8rem; text-decoration: none; }
.nav-footer a:hover { color: #fff; }

/* Main content */
.content {
  margin-left: var(--sidebar-w);
  flex: 1;
  padding: 32px;
  max-width: 960px;
  width: 100%;
}

/* Menu toggle (mobile) */
.menu-toggle {
  display: none;
  position: fixed;
  top: 12px; left: 12px;
  z-index: 200;
  background: var(--sidebar-bg);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  padding: 8px 12px;
  font-size: 1.2rem;
  cursor: pointer;
}

/* Ad slots */
.ad-slot { margin: 16px 0; }
.ad-placeholder {
  background: var(--surface);
  border: 1px dashed var(--border);
  border-radius: var(--radius);
  padding: 12px;
  text-align: center;
  min-height: 60px;
  display: flex;
  align-items: center;
  justify-content: center;
}
.ad-label { color: var(--text-muted); font-size: 0.75rem; text-transform: uppercase; letter-spacing: 1px; }

/* Cards */
.tool-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 16px;
  margin-top: 24px;
}
.tool-card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  text-decoration: none;
  color: var(--text);
  box-shadow: var(--shadow);
  transition: box-shadow 0.2s, transform 0.15s;
}
.tool-card:hover { box-shadow: 0 4px 12px rgba(0,0,0,0.1); transform: translateY(-2px); }
.tool-card-icon { font-size: 1.5rem; margin-bottom: 8px; display: block; }
.tool-card h3 { font-size: 1rem; margin-bottom: 4px; }
.tool-card p { font-size: 0.85rem; color: var(--text-muted); }

/* Tool page common */
.tool-header { margin-bottom: 24px; }
.tool-header h1 { font-size: 1.5rem; margin-bottom: 4px; }
.tool-header p { color: var(--text-muted); }

.tool-panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 24px;
  box-shadow: var(--shadow);
  margin-bottom: 16px;
}

textarea, input[type="text"], input[type="number"], select {
  width: 100%;
  padding: 10px 14px;
  border: 1px solid var(--border);
  border-radius: var(--radius);
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 0.88rem;
  background: var(--bg);
  color: var(--text);
  resize: vertical;
  transition: border-color 0.15s;
}
textarea:focus, input:focus, select:focus {
  outline: none;
  border-color: var(--primary);
}
textarea { min-height: 140px; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 6px;
  padding: 8px 18px;
  background: var(--primary);
  color: #fff;
  border: none;
  border-radius: var(--radius);
  font-size: 0.88rem;
  cursor: pointer;
  transition: background 0.15s;
}
.btn:hover { background: var(--primary-hover); }
.btn-secondary { background: #6b7280; }
.btn-secondary:hover { background: #4b5563; }

.btn-row { display: flex; gap: 8px; margin: 12px 0; flex-wrap: wrap; }

label {
  display: block;
  font-size: 0.85rem;
  font-weight: 600;
  margin-bottom: 6px;
  color: var(--text-muted);
}

.output-box {
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 14px;
  font-family: 'SF Mono', 'Fira Code', monospace;
  font-size: 0.85rem;
  white-space: pre-wrap;
  word-break: break-all;
  min-height: 60px;
  margin-top: 8px;
}

.inline-group {
  display: flex;
  gap: 12px;
  align-items: end;
  flex-wrap: wrap;
  margin-bottom: 12px;
}
.inline-group > div { flex: 1; min-width: 120px; }

.status-msg {
  font-size: 0.8rem;
  padding: 6px 12px;
  border-radius: var(--radius);
  margin-top: 8px;
  display: none;
}
.status-msg.success { display: block; background: #d1fae5; color: #065f46; }
.status-msg.error { display: block; background: #fee2e2; color: #991b1b; }

/* Home hero */
.hero { margin-bottom: 8px; }
.hero h1 { font-size: 2rem; margin-bottom: 8px; }
.hero p { color: var(--text-muted); font-size: 1.05rem; max-width: 540px; }

/* Markdown preview */
.md-preview {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 20px;
  min-height: 200px;
}
.md-preview h1, .md-preview h2, .md-preview h3 { margin: 16px 0 8px; }
.md-preview p { margin: 8px 0; }
.md-preview code { background: var(--bg); padding: 2px 6px; border-radius: 4px; font-size: 0.88em; }
.md-preview pre { background: var(--bg); padding: 14px; border-radius: var(--radius); overflow-x: auto; }
.md-preview pre code { background: none; padding: 0; }
.md-preview ul, .md-preview ol { padding-left: 24px; margin: 8px 0; }
.md-preview blockquote { border-left: 3px solid var(--primary); padding-left: 14px; color: var(--text-muted); margin: 12px 0; }

/* Color picker */
.color-swatch {
  width: 80px;
  height: 80px;
  border-radius: var(--radius);
  border: 2px solid var(--border);
  cursor: pointer;
}
.color-values { display: flex; gap: 12px; flex-wrap: wrap; margin-top: 12px; }
.color-values div { flex: 1; min-width: 140px; }

/* QR code */
.qr-output { text-align: center; margin-top: 16px; }
.qr-output canvas { max-width: 256px; }

/* Unit converter */
.converter-row { display: flex; gap: 12px; align-items: end; margin-bottom: 16px; flex-wrap: wrap; }
.converter-row > div { flex: 1; min-width: 140px; }
.swap-btn { font-size: 1.2rem; background: transparent; border: 1px solid var(--border); padding: 8px; border-radius: var(--radius); cursor: pointer; align-self: end; }

/* Password strength */
.strength-bar { height: 6px; border-radius: 3px; background: var(--border); margin-top: 8px; overflow: hidden; }
.strength-bar div { height: 100%; transition: width 0.3s; }

/* Footer */
.site-footer { margin-top: 40px; padding-top: 16px; border-top: 1px solid var(--border); text-align: center; color: var(--text-muted); font-size: 0.8rem; }

/* Privacy */
.prose h2 { margin-top: 24px; }
.prose p { margin: 8px 0; }

/* Responsive */
@media (max-width: 768px) {
  .sidebar { transform: translateX(-100%); }
  .sidebar.open { transform: translateX(0); }
  .menu-toggle { display: block; }
  .content { margin-left: 0; padding: 60px 16px 24px; }
}