.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: var(--space-3) var(--space-5);
  border-radius: var(--radius-md);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  font-weight: 600;
  line-height: 1;
  cursor: pointer;
  border: none;
  transition: background var(--transition-fast), box-shadow var(--transition-fast), opacity var(--transition-fast), transform var(--transition-fast);
  text-decoration: none;
  white-space: nowrap;
  user-select: none;
}

.btn:active {
  transform: translateY(1px);
}

.btn:disabled,
.btn[disabled] {
  opacity: 0.4;
  cursor: not-allowed;
  pointer-events: none;
}

/* Primary */
.btn-primary {
  background: var(--color-accent);
  color: #1A1030;
  box-shadow: var(--shadow-sm);
}

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

/* Secondary */
.btn-secondary {
  background: var(--color-card);
  color: var(--color-text-primary);
  border: 1px solid var(--color-border);
}

.btn-secondary:hover:not(:disabled) {
  background: var(--color-card-raised);
  border-color: var(--color-accent);
  box-shadow: var(--shadow-sm);
}

/* Ghost */
.btn-ghost {
  background: transparent;
  color: var(--color-text-secondary);
  border: 1px solid transparent;
}

.btn-ghost:hover:not(:disabled) {
  background: var(--color-accent-dim);
  color: var(--color-text-primary);
  border-color: var(--color-border);
}

/* Danger */
.btn-danger {
  background: var(--color-error-bg);
  color: var(--color-error);
  border: 1px solid rgba(255, 123, 123, 0.3);
}

.btn-danger:hover:not(:disabled) {
  background: rgba(255, 123, 123, 0.2);
}

/* Sizes */
.btn-sm {
  padding: var(--space-2) var(--space-3);
  font-size: var(--text-xs);
  border-radius: var(--radius-sm);
}

.btn-lg {
  padding: var(--space-4) var(--space-8);
  font-size: var(--text-base);
  border-radius: var(--radius-md);
}

/* Icon-only button */
.btn-icon {
  width: 36px;
  height: 36px;
  padding: 0;
  border-radius: var(--radius-full);
}

.btn-icon.btn-sm {
  width: 28px;
  height: 28px;
}

/* Loading state */
.btn.loading {
  pointer-events: none;
  position: relative;
  color: transparent;
}

.btn.loading::after {
  content: '';
  position: absolute;
  width: 14px;
  height: 14px;
  border: 2px solid transparent;
  border-top-color: currentColor;
  border-radius: 50%;
  animation: btn-spin 0.6s linear infinite;
  color: #1A1030;
}

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