/* ============================================================================
   KK Intent OS · base layer
   Reset + accessibility floor. No concept-specific rules live here.
   ========================================================================== */

*, *::before, *::after { box-sizing: border-box; }

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg, #070A10);
  color: var(--text, #F2F6FA);
  font-family: var(--f-sans);
  font-size: var(--fs-16);
  line-height: var(--lh-body);
  -webkit-font-smoothing: antialiased;
}

/* ---- touch behaviour: the app contract, stated once ----------------------
   `manipulation` on the root is the intersection baseline for the whole tree
   (touch-action is intersected with every ancestor), so it grants immediate
   tap delivery — no 300 ms double-tap-to-zoom wait — while still allowing
   pan and pinch-zoom. A descendant can only ever narrow this, never widen it,
   so `touch-action: none` on a drag handle keeps working. */
html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  -webkit-tap-highlight-color: transparent;
  touch-action: manipulation;
}

body {
  min-height: 100vh;
  /* The field canvas is fixed; the OS shell scrolls above it.
     `clip`, not `hidden`: on Chrome `overflow-x: hidden` makes <body> a scroll
     container, and a ScrollTrigger pin then measures position:fixed against the
     wrong box. `clip` refuses the overflow without creating a scroller, so
     <html> stays the only one. */
  overflow-x: clip;
}

/* ---- modal scroll lock ---------------------------------------------------
   A sheet is modal in behaviour, so the page behind it must not move: with the
   document still live, a finger on the sheet's edge drags the whole page and
   that reads as a broken app, not as a sheet.

   Locking by `overflow: hidden` alone would clamp the offset to 0 and jump the
   page to the top, so the body is pinned instead and `top` carries the saved
   offset (set by os.js). Restoring the offset on unlock puts the reader back
   exactly where they were. */
html[data-locked="true"] {
  overflow: hidden;
  overscroll-behavior: none;
}
html[data-locked="true"] body {
  position: fixed;
  left: 0;
  right: 0;
  width: 100%;
  overflow: hidden;
}

/* Independent scrollers must not hand their overscroll to the page. */
.sheet,
.term,
[data-scroll-contain] { overscroll-behavior: contain; }

/* ---- deep links must not land under the fixed bar ------------------------
   Every surface publishes its own bar height as --stick-offset; without this a
   `#section` jump parks the heading behind the glass bar. */
[id] { scroll-margin-top: calc(var(--stick-offset, 96px) + var(--s-4, 16px)); }

h1, h2, h3, p, ul, ol, figure { margin: 0; }
ul, ol { padding: 0; list-style: none; }

a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 3px; }
a:hover { color: var(--text); }

button, input, textarea, select { font: inherit; color: inherit; }

/* ---- visible focus, always ---- */
:focus-visible {
  outline: var(--focus-w) solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

/* ---- every interactive control clears 44px ---- */
.btn {
  min-height: var(--touch);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--s-2);
  padding: 0 var(--s-4);
  border: 1px solid var(--line);
  border-radius: var(--r-s);
  background: var(--surface-2);
  color: var(--text);
  font-size: var(--fs-14);
  font-weight: 600;
  cursor: pointer;
  transition: background var(--dur) var(--ease), border-color var(--dur) var(--ease), transform var(--dur-fast) var(--ease);
}
.btn:hover { border-color: var(--line-strong); }
.btn:active { transform: translateY(1px); }
.btn[disabled], .btn[aria-disabled="true"] { opacity: .5; cursor: not-allowed; }

.btn--primary {
  background: var(--accent);
  border-color: transparent;
  color: var(--accent-ink);
}
.btn--primary:hover { filter: brightness(1.06); border-color: transparent; }

.btn--ghost { background: transparent; }

/* Footer nav — the way back out of each surface.
   Every item is a .btn, so it already clears 44px; wrapping (not overflowing)
   is what keeps this usable at 320px now that each page carries two links.
   Added in round 7: the two concept pages had no exit at all, so a reader who
   arrived from the homepage could only leave with the browser's Back button. */
.footnav {
  display: flex;
  flex-wrap: wrap;
  gap: var(--s-3);
  margin-bottom: var(--s-5);
}

/* Text links that act as controls still need a 44px hit area. */
.linkbtn {
  min-height: var(--touch);
  display: inline-flex;
  align-items: center;
  padding: 0 var(--s-2);
  background: none;
  border: 0;
  color: var(--accent);
  cursor: pointer;
  text-align: left;
}
.linkbtn:hover { text-decoration: underline; }

/* ---- a11y helpers ---- */
.sr-only {
  position: absolute; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0 0 0 0); clip-path: inset(50%); white-space: nowrap; border: 0;
}
.skip-link {
  position: absolute; left: 50%; top: -100px; transform: translateX(-50%);
  z-index: var(--z-toast);
  background: var(--accent); color: var(--accent-ink);
  padding: var(--s-3) var(--s-4); border-radius: var(--r-s);
  font-size: var(--fs-14); font-weight: 700; text-decoration: none;
  transition: top var(--dur) var(--ease);
}
.skip-link:focus { top: 8px; }

/* ---- shared type utilities ---- */
.eyebrow {
  font-family: var(--f-mono);
  font-size: var(--fs-12);
  letter-spacing: .14em;
  text-transform: uppercase;
  color: var(--accent);
}
.lead { font-size: var(--fs-16); color: var(--text-soft); }
.mono { font-family: var(--f-mono); font-size: var(--fs-12); }

/* ---- reduced motion: kill every transition, the field stops drifting ---- */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: .001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: .001ms !important;
    scroll-behavior: auto !important;
  }
}