Primary, secondary, ghost, and danger variants with size options.
<button class="btn btn-primary">Primary</button>
<button class="btn btn-secondary">Secondary</button>
<button class="btn btn-ghost">Ghost</button>
<button class="btn btn-danger">Danger</button>
<button class="btn btn-primary" disabled>Disabled</button>
<!-- Sizes -->
<button class="btn btn-primary btn-sm">Small</button>
<button class="btn btn-primary">Medium</button>
<button class="btn btn-primary btn-lg">Large</button>
<button class="btn btn-primary btn-block">Full Width</button>