/* Calm transitions and clearly labelled, comfortable navigation. */
:root {
  --motion-fast: 180ms;
  --motion-ease: cubic-bezier(.2, .7, .2, 1);
}

@view-transition {
  navigation: auto;
}

/* Cross-fade the reading area while the header stays in place. */
main { view-transition-name: reading-page; }
::view-transition-group(*) { animation-duration: 200ms; }
::view-transition-old(root),
::view-transition-new(root) { animation: none; }
::view-transition-old(reading-page) {
  animation: 160ms ease-out both plaintech-fade-out;
}
::view-transition-new(reading-page) {
  animation: 200ms ease-in both plaintech-fade-in;
}
@keyframes plaintech-fade-in { from { opacity: 0; } to { opacity: 1; } }
@keyframes plaintech-fade-out { from { opacity: 1; } to { opacity: 0; } }

.menu-button,
.nav a,
.outline-button,
.solid-button,
.search-big button,
.save-button,
.filter,
.choice-tab,
.topic-link,
.start-link,
.step,
.lesson-row,
.symptom-card,
.device-card {
  transition: background-color var(--motion-fast) var(--motion-ease),
              border-color var(--motion-fast) var(--motion-ease),
              color var(--motion-fast) var(--motion-ease),
              box-shadow var(--motion-fast) var(--motion-ease);
}
.guide-card,
.intent-card,
.route-card {
  transition-duration: 220ms;
  transition-timing-function: var(--motion-ease);
}
[data-choice-panel]:not([hidden]),
details[open] > p,
.toast:not([hidden]) {
  animation: plaintech-fade-in var(--motion-fast) ease-out;
}
.saved-nav-label { display: none; }

@media (max-width: 760px) {
  .menu-button {
    align-items: center;
    justify-content: center;
    gap: 8px;
    min-height: 44px;
    padding: 9px 12px;
    border: 1px solid #b6c5ab;
    border-radius: 7px;
    background: var(--paper);
    color: var(--green);
    font-size: 16px;
    font-weight: 600;
    line-height: 1.3;
    white-space: nowrap;
  }
  .menu-button:hover,
  .menu-button[aria-expanded="true"] {
    background: var(--sage);
    border-color: var(--green);
  }
  .nav,
  .nav.is-open {
    display: grid;
    grid-template-columns: repeat(2, minmax(0, 1fr));
    gap: 6px 12px;
    padding: 14px 21px 18px;
    max-height: calc(100vh - 70px);
    max-height: calc(100dvh - 70px);
    overflow-y: auto;
    font-size: 16px;
    box-shadow: 0 10px 20px #244b3018;
    opacity: 0;
    visibility: hidden;
    transform: translateY(-4px);
    pointer-events: none;
    transition: opacity var(--motion-fast) var(--motion-ease),
                transform var(--motion-fast) var(--motion-ease),
                visibility 0s var(--motion-fast);
  }
  .nav.is-open {
    opacity: 1;
    visibility: visible;
    transform: translateY(0);
    pointer-events: auto;
    transition-delay: 0s;
  }
  .nav a {
    display: flex;
    align-items: center;
    min-height: 48px;
    padding: 10px 12px;
    border-radius: 6px;
  }
  .nav a:hover,
  .nav a:focus-visible,
  .nav a[aria-current="page"] { background: var(--sage); }
  .nav .saved-nav { gap: 8px; padding-left: 12px; }
  .saved-nav-label { display: inline; }
}

@media (max-width: 420px) {
  .nav, .nav.is-open { grid-template-columns: 1fr; gap: 2px; }
}

@media (max-width: 360px) {
  .header-inner { gap: 10px; }
  .header .brand { gap: 8px; font-size: 26px; }
  .header .brand svg { width: 24px; }
}

@media (prefers-reduced-motion: reduce) {
  @view-transition { navigation: none; }
  *, *::before, *::after {
    animation: none !important;
    transition: none !important;
    scroll-behavior: auto !important;
  }
  ::view-transition-group(*),
  ::view-transition-old(*),
  ::view-transition-new(*) { animation: none !important; }
}