/* Presentation shell.
 * Sits on top of tokens.css + base.css, under theme-field-guide.css.
 * Only contains layout, the slide scale, and section-transition rules that the
 * base stylesheet does not provide. All colours come from the theme.
 */

/* ═══════════ THE SLIDE SCALE ═══════════
 *
 * A slide is one viewport tall, so its type is sized from viewport HEIGHT — not
 * fixed pixels. This is the decision the whole type system rests on, and it exists
 * because three requirements are otherwise incompatible: nothing on a slide may
 * be smaller than 14px, nothing may overflow, and no content may be cut to make
 * room.
 *
 * Fixed pixels can satisfy any two of those. Raising an 11px floor to 14px in a
 * fixed scale pushes the dense slides past the bottom of the screen, and the
 * only fixed-pixel escapes are cutting words or accepting a scrollbar mid-talk.
 * A height-relative scale satisfies all three: the deck keeps its proportions on
 * whatever the venue projector turns out to be, and the type grows with the
 * room instead of being tuned for one laptop.
 *
 * Every size is clamped at both ends:
 *   - the LOWER bound is the legibility floor. It is what makes the 14px
 *     minimum and 16px body true even on a short window.
 *   - the UPPER bound stops the type ballooning on a 4K display or a very tall
 *     browser window, where pure vh would produce headlines nobody asked for.
 *
 * The vh figures are derived from the approved design exploration, which
 * expressed the same scale as a fraction of slide height. Reference column is
 * a 1920×1080 screen, where the stage is ~967px tall after the header and nav
 * bar — the resolution the deck is presented at.
 *
 * Line heights are unitless on purpose, so they track the font size instead of
 * being a second set of numbers to keep in sync.
 */
:root {
  /*                    floor      height-relative   ceiling        @1080p */
  --ae-fs-display: clamp(40px,      7.48vh,          104px);     /* ~81px */
  --ae-lh-display: 1.04;
  --ae-fs-h1:      clamp(34px,      5.33vh,           76px);     /* ~58px */
  --ae-lh-h1:      1.05;
  --ae-fs-h2:      clamp(24px,      3.19vh,           44px);     /* ~34px */
  --ae-lh-h2:      1.12;
  --ae-fs-h3:      clamp(20px,      2.54vh,           34px);     /* ~27px */
  --ae-lh-h3:      1.20;
  --ae-fs-h4:      clamp(17px,      2.20vh,           28px);     /* ~24px */
  --ae-lh-h4:      1.30;
  --ae-fs-h5:      clamp(16px,      1.90vh,           24px);     /* ~21px */
  --ae-lh-h5:      1.35;
  --ae-fs-lead:    clamp(19px,      2.54vh,           34px);     /* ~27px */
  --ae-lh-lead:    1.50;
  --ae-fs-body:    clamp(16px,      2.04vh,           26px);     /* ~22px */
  --ae-lh-body:    1.45;
  --ae-fs-small:   clamp(15px,      1.81vh,           23px);     /* ~20px */
  --ae-lh-small:   1.45;
  /* The floor. Nothing on a slide is allowed to be smaller than this. */
  --ae-fs-caption: clamp(14px,      1.62vh,           20px);     /* ~17px */
  --ae-lh-caption: 1.40;

  /* Spacing tracks the same axis, or the rhythm drifts as the type grows.
   * 1 and 2 stay fixed: they are hairline gaps, not layout. */
  --ae-space-3: clamp(8px,   1.1vh, 14px);
  --ae-space-4: clamp(10px,  1.5vh, 18px);
  --ae-space-5: clamp(14px,  2.1vh, 26px);
  --ae-space-6: clamp(18px,  2.9vh, 36px);
  --ae-space-7: clamp(24px,  4.0vh, 50px);
  --ae-space-8: clamp(30px,  5.2vh, 66px);
  --ae-space-9: clamp(40px,  7.4vh, 96px);

  /* Slide side padding scales with WIDTH — it is a horizontal measure. */
  --ae-gutter: clamp(20px, 3.4vw, 64px);
}

/* The deck's own floor, exposed so a slide can reason about it rather than
 * guessing a pixel value. Anything smaller is a bug, not a style choice. */
:root { --fg-fs-floor: var(--ae-fs-caption); }

html, body { height: 100%; overflow: hidden; }
body { display: flex; flex-direction: column; background: var(--ae-bg); }

/* ═══════════ CHROME ═══════════
 *
 * The header and nav bar are deliberately sized in FIXED pixels, not the slide
 * scale. Two reasons: chrome that grows with viewport height steals the height
 * the slide needs, and chrome is not slide content — the 14px floor is a
 * promise about what the audience has to read, and nobody in row twenty is
 * reading the language toggle.
 *
 * Chrome is quiet: paper ground, hairline separators, one accent for state.
 */

/* ───── Header ───── */
#header {
  flex-shrink: 0;
  z-index: 50;
  background: var(--fg-paper);
  border-bottom: 1px solid var(--fg-hair);
}
#header .header-inner {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  min-height: 54px;
  gap: var(--ae-space-5);
}
#header .ae-header__brand { justify-self: start; }
#header .ae-header__brand .brand-logo {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 24px; height: 24px;
  border-radius: var(--ae-radius-sm);
  background: var(--fg-green);
  color: #fff;
  /* A chevron is a glyph, not code — it does not get the mono face. */
  font-family: var(--ae-font);
  font-weight: 600;
  font-size: 15px;
  line-height: 1;
  flex-shrink: 0;
}
#header .ae-header__brand .brand-name {
  font-family: var(--ae-font-head);
  font-size: 16px;
  font-weight: 700;
  letter-spacing: -0.012em;
  color: var(--fg-ink);
  white-space: nowrap;
}
#header .page-title {
  justify-self: center;
  font-family: var(--ae-font);
  font-size: 14px;
  font-weight: 500;
  color: var(--fg-muted);
  white-space: nowrap;
  overflow: hidden;
  text-overflow: ellipsis;
  max-width: 60ch;
}
#header .header-right { justify-self: end; }
#header .lang-toggle {
  display: inline-flex;
  border: 1px solid var(--fg-hair);
  border-radius: 999px;
  overflow: hidden;
  background: var(--fg-card);
}
#header .lang-toggle button {
  font-family: var(--ae-font);
  font-size: 12.5px;
  font-weight: 600;
  letter-spacing: 0.03em;
  padding: 5px 12px;
  border: 0;
  background: transparent;
  color: var(--fg-muted);
  cursor: pointer;
  transition: background 160ms var(--ae-ease), color 160ms var(--ae-ease);
}
#header .lang-toggle button + button { border-left: 1px solid var(--fg-hair); }
#header .lang-toggle button:hover { color: var(--fg-ink); background: var(--ae-cool-gray-100); }
#header .lang-toggle button.active { background: var(--fg-green); color: #fff; }

/* ───── Stage (where sections mount) ───── */
#stage {
  flex: 1;
  position: relative;
  overflow: hidden;
  min-height: 0;
  background: var(--ae-bg);
}
#stage > * {
  position: absolute;
  inset: 0;
  display: block;
  opacity: 1;
  transform: translateY(0);
  transition:
    opacity   400ms var(--ae-ease),
    transform 400ms var(--ae-ease);
  /* Sections center their content vertically. Without `safe`, flex
     centering clips overflowing content at both ends and breaks scrolling.
     `safe center` falls back to flex-start when content exceeds the
     viewport — the slide top stays visible and the rest can be scrolled. */
  justify-content: safe center;
}
#stage > *.entering { opacity: 0; transform: translateY(14px); }
#stage > *.exiting  { opacity: 0; transform: translateY(-14px); }

/* ───── Nav bar ───── */
#nav {
  position: relative;
  flex-shrink: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 20px;
  padding: 10px var(--ae-gutter);
  background: var(--fg-paper);
  border-top: 1px solid var(--fg-hair);
}
#nav .ae-btn {
  font-size: 13px;
  padding: 6px 16px;
  min-height: 34px;
}
/* Scoped to #nav as well, or the rule above wins on specificity (1-1-0 beats
 * 1-0-0) and its horizontal padding squeezes the icon to zero width. */
#nav #btn-fullscreen {
  position: absolute;
  right: var(--ae-gutter);
  top: 50%;
  transform: translateY(-50%);
  width: 34px;
  min-height: 34px;
  padding: 0;
}
#nav #btn-fullscreen svg { width: 17px; height: 17px; display: block; }
#counter {
  font-family: var(--ae-font);
  font-size: 13px;
  font-weight: 600;
  color: var(--fg-muted);
  min-width: 64px;
  text-align: center;
  font-variant-numeric: tabular-nums;
}

#chapters {
  display: flex;
  gap: 6px;
  flex-wrap: wrap;
  justify-content: center;
}
#chapters button {
  font-family: var(--ae-font);
  font-size: 12.5px;
  font-weight: 500;
  letter-spacing: 0.01em;
  padding: 5px 13px;
  border: 1px solid var(--fg-hair);
  background: var(--fg-card);
  color: var(--fg-muted);
  border-radius: 999px;
  cursor: pointer;
  transition: background 180ms var(--ae-ease),
              color 180ms var(--ae-ease),
              border-color 180ms var(--ae-ease);
}
#chapters button:hover {
  border-color: var(--ae-cool-gray-400);
  color: var(--fg-ink);
}
#chapters button.current {
  background: var(--fg-green);
  border-color: var(--fg-green);
  color: #fff;
  font-weight: 600;
}
#chapters button .key {
  margin-left: 6px;
  padding: 0 5px;
  border: 1px solid currentColor;
  border-radius: 3px;
  opacity: 0.55;
  font-size: 0.78em;
  font-weight: 700;
}

@media (max-width: 600px) {
  #header .header-inner { min-height: 48px; }
  #header .page-title { font-size: 12.5px; }
  #header .ae-header__brand .brand-name { display: none; }
  #btn-fullscreen { display: none; }
}

/* ───── Section conventions ───── */
/* Bold spans inside any section's lede carry the accent, deck-wide. Kept on
 * both the legacy .lede class and the slide kit's .fg-lede while the slides
 * are converted. */
.lede b, .fg-lede b { color: var(--fg-green-d); font-weight: 600; }

/* ───── Reduced motion ─────
 * Sections animate their content in with per-element delays. With reduced
 * motion, collapse every animation/transition to a single instant frame:
 * `forwards` fill still applies, so slides render fully revealed. Infinite
 * pulse loops are clamped to one iteration. */
@media (prefers-reduced-motion: reduce) {
  #stage *, #stage *::before, #stage *::after {
    animation-duration: 1ms !important;
    animation-delay: 0ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 1ms !important;
  }
}