:root {
  --color-bg:          #f8fafc;
  --color-surface:     #ffffff;
  --color-surface-2:   #f1f5f9;
  --color-border:      #dbe3ee;
  --color-text:        #0f172a;
  --color-text-muted:  #64748b;
  --color-accent:      #3b82f6;
  --color-accent-dark: #2563eb;
  --color-success:     #16a34a;
  --color-error:       #dc2626;
  --color-warning:     #d97706;

  --font-sans: "Inter", system-ui, -apple-system, sans-serif;
  --font-mono: "JetBrains Mono", "Fira Code", monospace;

  --space-1:  4px;
  --space-2:  8px;
  --space-3: 12px;
  --space-4: 16px;
  --space-5: 20px;
  --space-6: 24px;
  --space-8: 32px;

  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
}

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

html, body {
  height: 100%;
  background: var(--color-bg);
  color: var(--color-text);
  font-family: var(--font-sans);
  font-size: 15px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
}

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

.navbar {
  display: flex;
  align-items: center;
  gap: var(--space-6);
  padding: 0 var(--space-8);
  height: 56px;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  position: sticky;
  top: 0;
  z-index: 100;
}

.navbar__brand {
  font-weight: 700;
  font-size: 17px;
  letter-spacing: -.3px;
  color: var(--color-accent);
  white-space: nowrap;
}

.navbar__links {
  display: flex;
  gap: var(--space-2);
  list-style: none;
}

.navbar__link {
  padding: var(--space-2) var(--space-3);
  border-radius: var(--radius-sm);
  color: var(--color-text-muted);
  font-size: 14px;
  font-weight: 500;
  transition: color .15s, background .15s;
}

.navbar__link:hover {
  color: var(--color-text);
  background: var(--color-surface-2);
  text-decoration: none;
}

.navbar__link--active {
  color: var(--color-accent);
  background: var(--color-surface-2);
}

.main {
  padding: var(--space-6) var(--space-8);
  max-width: 1400px;
  margin: 0 auto;
}

.main--narrow {
  max-width: 600px;
}

.alert {
  padding: var(--space-4) var(--space-5);
  border-radius: var(--radius-md);
  margin-bottom: var(--space-5);
  font-size: 14px;
  line-height: 1.5;
}

.alert--success {
  background: #f0fdf4;
  border: 1px solid #86efac;
  color: #166534;
}

.alert--error {
  background: #fef2f2;
  border: 1px solid #fca5a5;
  color: #991b1b;
}

.hidden { display: none !important; }

.spinner {
  display: inline-block;
  width: 28px;
  height: 28px;
  border: 3px solid var(--color-border);
  border-top-color: var(--color-accent);
  border-radius: 50%;
  animation: spin .8s linear infinite;
}

@keyframes spin { to { transform: rotate(360deg); } }

.btn {
  display: inline-flex;
  align-items: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-sm);
  font-size: 14px;
  font-weight: 600;
  cursor: pointer;
  border: none;
  transition: opacity .15s, transform .1s;
}

.btn:active { transform: scale(.97); }
.btn:disabled { opacity: .5; cursor: not-allowed; }

.btn--primary {
  background: var(--color-accent);
  color: #fff;
}

.btn--primary:hover:not(:disabled) {
  background: var(--color-accent-dark);
}