/*
 * components/panels.css — Panel component: static section panel + the
 * collapsible variant (Session 4).
 *
 * Paired with the `panel()`/`collapsible_panel()` macros in
 * templates/components/panels.html and the toggle enhancement in
 * static/js/components/panels.js.
 */

.panel {
  background: var(--color-surface);
  border: var(--border-1);
  border-radius: var(--radius-md);
  box-shadow: var(--shadow-sm);
  margin-bottom: var(--space-4);
  animation: panel-in var(--dur-base) var(--ease-standard);
}

@keyframes panel-in {
  from { opacity: 0; transform: translateY(4px); }
  to { opacity: 1; transform: translateY(0); }
}

.panel__head {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  border-bottom: var(--border-1);
}

.panel__head h3,
.panel__head h2 {
  margin: 0;
  font-size: var(--fs-md);
}

.panel__body {
  padding: var(--space-4);
}

/* Collapsible panel: a button-controlled disclosure region (panels.js),
   used where a native <details> element is not appropriate (e.g. the
   header needs its own actions alongside the toggle). */

.panel--collapsible .panel__head {
  border-bottom: none;
  padding: 0;
}

.panel-toggle {
  appearance: none;
  border: none;
  background: transparent;
  width: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-3);
  padding: var(--space-3) var(--space-4);
  font: inherit;
  font-size: var(--fs-md);
  font-weight: var(--fw-semibold);
  color: var(--color-fg);
  cursor: pointer;
  border-radius: var(--radius-md);
}

.panel-toggle:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: -2px;
}

.panel-toggle__icon {
  flex: none;
  transition: transform var(--dur-fast) var(--ease-standard);
  color: var(--color-fg-muted);
}

.panel-toggle[aria-expanded="true"] .panel-toggle__icon {
  transform: rotate(90deg);
}

.panel__collapse-body {
  padding: 0 var(--space-4) var(--space-4);
}

.panel__collapse-body[hidden] {
  display: none;
}

@media (prefers-reduced-motion: reduce) {
  .panel-toggle__icon {
    transition: none;
  }
  .panel {
    animation: none;
  }
}