/*
 * Unified Button Component System — Editorial
 * ===========================================
 * Calm solid backgrounds. Ink primary. Emerald accent. 1px borders.
 * No transform lift, no gradient, no glow.
 */

/* ==========================================
 * BASE BUTTON STYLES
 * ========================================== */

.btn {
  box-sizing: border-box;
  -webkit-appearance: none;
  appearance: none;

  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);

  padding: var(--space-3) var(--space-5);
  min-height: 40px;

  font-family: var(--font-sans);
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  line-height: 1;
  text-align: center;
  text-decoration: none;
  white-space: nowrap;

  border: var(--border-width-1) solid transparent;
  border-radius: var(--btn-border-radius);
  cursor: pointer;

  transition:
    background-color var(--transition-default),
    border-color var(--transition-default),
    color var(--transition-default);

  user-select: none;
  -webkit-user-select: none;
}

.btn:focus { outline: none; }
.btn:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 2px;
}

/* ==========================================
 * BUTTON VARIANTS
 * ========================================== */

/* Primary — ink */
.btn-primary {
  background: var(--ink);
  color: var(--paper);
  border-color: var(--ink);
}
.btn-primary:hover  { background: var(--ink-secondary); border-color: var(--ink-secondary); }
.btn-primary:active { background: var(--ink-pressed); }

/* Accent — emerald (used for CTAs that need brand emphasis) */
.btn-accent {
  background: var(--accent);
  color: var(--paper);
  border-color: var(--accent);
}
.btn-accent:hover  { background: var(--accent-hover); border-color: var(--accent-hover); }
.btn-accent:active { background: var(--emerald-700); }

/* Secondary — quiet sans, no border */
.btn-secondary {
  background: transparent;
  color: var(--ink-muted);
  border-color: transparent;
}
.btn-secondary:hover  { background: var(--paper-warm); color: var(--ink); }
.btn-secondary:active { background: var(--paper-sunken); }

/* Outline — hairline border, ink fill on hover */
.btn-outline {
  background: transparent;
  color: var(--ink);
  border-color: var(--line-strong);
}
.btn-outline:hover  { background: var(--paper-warm); border-color: var(--ink); }
.btn-outline:active { background: var(--paper-sunken); }
.btn-outline.active { background: var(--ink); color: var(--paper); border-color: var(--ink); }

/* Outline Secondary — muted ink */
.btn-outline-secondary {
  background: transparent;
  color: var(--ink-muted);
  border-color: var(--line-strong);
}
.btn-outline-secondary:hover  { background: var(--paper-warm); color: var(--ink); border-color: var(--ink); }
.btn-outline-secondary:active { background: var(--paper-sunken); }

/* Success — emerald (positive change is the brand) */
.btn-success {
  background: var(--accent);
  color: var(--paper);
  border-color: var(--accent);
}
.btn-success:hover  { background: var(--accent-hover); border-color: var(--accent-hover); }
.btn-success:active { background: var(--emerald-700); }

/* Danger — terracotta */
.btn-danger {
  background: var(--negative);
  color: var(--paper);
  border-color: var(--negative);
}
.btn-danger:hover  { background: var(--negative-strong); border-color: var(--negative-strong); }
.btn-danger:active { background: var(--negative-pressed); }

/* Ghost — bare */
.btn-ghost {
  background: transparent;
  color: var(--ink);
  border-color: transparent;
}
.btn-ghost:hover  { background: var(--paper-warm); }
.btn-ghost:active { background: var(--paper-sunken); }

/* Upgrade — premium brass pill */
.btn-upgrade {
  background: var(--premium);
  color: var(--paper);
  border-color: var(--premium);
  border-radius: 100px;
  letter-spacing: 0.01em;
  font-size: var(--font-size-sm);
  font-weight: var(--font-weight-medium);
  padding: var(--space-2) var(--space-5);
  min-height: 32px;
}
.btn-upgrade:hover  { background: var(--premium-strong); border-color: var(--premium-strong); }
.btn-upgrade:active { background: var(--premium-pressed); }

/* ==========================================
 * BUTTON SIZES
 * ========================================== */

.btn-sm {
  padding: var(--space-2) var(--space-4);
  font-size: var(--font-size-sm);
  min-height: 32px;
}

.btn-lg {
  padding: var(--space-4) var(--space-6);
  font-size: var(--font-size-base);
  min-height: 48px;
}

/* ==========================================
 * BUTTON MODIFIERS
 * ========================================== */

.btn-block { width: 100%; }

.btn-icon {
  padding: var(--space-3);
  min-width: 40px;
}

.btn-icon.btn-sm {
  padding: var(--space-2);
  min-width: 32px;
}

.btn-icon.btn-lg {
  padding: var(--space-4);
  min-width: 48px;
}

/* ==========================================
 * STATES
 * ========================================== */

.btn:disabled,
.btn.disabled {
  opacity: 0.5;
  cursor: not-allowed;
  pointer-events: none;
}

.btn.loading {
  position: relative;
  color: transparent;
  pointer-events: none;
}

.btn.loading::after {
  content: '';
  position: absolute;
  width: 14px;
  height: 14px;
  border: 1.5px solid currentColor;
  border-right-color: transparent;
  border-radius: var(--radius-full);
  animation: btn-spin 0.6s linear infinite;
}

.btn-primary.loading::after,
.btn-accent.loading::after,
.btn-success.loading::after,
.btn-danger.loading::after,
.btn-upgrade.loading::after {
  border-color: rgba(242, 239, 232, 0.35);
  border-right-color: transparent;
  border-top-color: var(--paper);
}

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

@media (prefers-reduced-motion: reduce) {
  .btn.loading::after { animation: none; }
}

/* ==========================================
 * BUTTON GROUPS
 * ========================================== */

.btn-group {
  display: inline-flex;
  gap: 0;
}

.btn-group .btn { border-radius: 0; }

.btn-group .btn:first-child {
  border-radius: var(--btn-border-radius) 0 0 var(--btn-border-radius);
}

.btn-group .btn:last-child {
  border-radius: 0 var(--btn-border-radius) var(--btn-border-radius) 0;
}

.btn-group .btn:not(:last-child) { border-right-width: 0; }
.btn-group .btn:not(:first-child):not(:last-child) { border-radius: 0; }

.btn-group-spaced {
  display: inline-flex;
  gap: var(--space-2);
}
.btn-group-spaced .btn { border-radius: var(--btn-border-radius); }

/* ==========================================
 * RESPONSIVE
 * ========================================== */

@media (max-width: 768px) {
  .btn {
    padding: var(--space-3) var(--space-4);
    font-size: var(--font-size-sm);
    min-height: 40px;
  }

  .btn-sm {
    padding: var(--space-2) var(--space-3);
    min-height: 30px;
  }

  .btn-lg {
    padding: var(--space-3) var(--space-5);
    font-size: var(--font-size-base);
    min-height: 44px;
  }
}