/* ============================================================================
   base.css — reset, typography, layout primitives, a11y
   Depends on tokens.css.
   ========================================================================== */

/* -- Reset ---------------------------------------------------------------- */

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

* { margin: 0; }

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
  /* Lenis drives scrolling; without it the anchor nav still needs an offset. */
  scroll-padding-top: calc(var(--nav-h) + 16px);
}

body {
  font-family: var(--font-vn);
  font-size: var(--fs-body);
  line-height: var(--leading-relaxed);
  color: var(--text-body);
  background: var(--bg-page);
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  overflow-x: hidden;
}

img,
picture,
video,
canvas,
svg {
  display: block;
  max-width: 100%;
}

img,
video { height: auto; }

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

button { background: none; border: 0; }

p,
h1, h2, h3, h4, h5, h6 { overflow-wrap: break-word; }

ul[role="list"],
ol[role="list"] { list-style: none; padding: 0; }

a { color: inherit; text-decoration: none; }

/* -- Focus ---------------------------------------------------------------- */

:focus-visible {
  outline: none;
  box-shadow: var(--page-ring, var(--ring));
  border-radius: var(--radius-sm);
}

.skip-link {
  position: absolute;
  top: 8px;
  left: 8px;
  z-index: 200;
  padding: 10px 18px;
  background: var(--yellow-500);
  color: var(--navy-900);
  font-weight: var(--weight-bold);
  border-radius: var(--radius-md);
  transform: translateY(-160%);
  transition: transform var(--dur-base) var(--ease-out-power3);
}

.skip-link:focus-visible { transform: translateY(0); }

.visually-hidden {
  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;
}

/* -- Layout primitives ---------------------------------------------------- */

.container {
  width: 100%;
  max-width: var(--container-max);
  margin-inline: auto;
  padding-inline: var(--gutter-sm);
}

@media (min-width: 768px) {
  .container { padding-inline: 48px; }
}

@media (min-width: 1200px) {
  .container { padding-inline: var(--gutter); }
}

/* Narrow measure for editorial copy — never let body copy run full width. */
.measure { max-width: 62ch; }
.measure-tight { max-width: 46ch; }
.measure-display { max-width: 18ch; }

.chapter {
  position: relative;
  padding-block: var(--chapter-pad-y);
  background: var(--page-bg);
  color: var(--page-fg);
  transition: background-color 0.6s var(--ease-out-power3),
              color 0.6s var(--ease-out-power3);
}

.chapter--flush { padding-block: 0; }

.stack > * + * { margin-top: var(--flow, var(--space-4)); }

.grid { display: grid; gap: var(--chapter-gap); }

@media (min-width: 900px) {
  .grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
  .grid-2-editorial { grid-template-columns: minmax(0, 5fr) minmax(0, 6fr); }
}

/* -- Typography ----------------------------------------------------------- */

.eyebrow {
  display: flex;
  align-items: center;
  gap: var(--space-3);
  font-family: var(--font-sans);
  font-size: var(--text-eyebrow);
  font-weight: var(--weight-bold);
  letter-spacing: var(--tracking-eyebrow);
  text-transform: uppercase;
  color: var(--page-eyebrow);
}

.eyebrow::before {
  content: "";
  width: 24px;
  height: 2px;
  background: currentColor;
  flex: none;
}

.eyebrow--plain::before { display: none; }

.chapter-num {
  font-family: var(--font-mono);
  font-size: var(--text-xs);
  font-weight: var(--weight-semibold);
  letter-spacing: 0.12em;
  color: var(--page-muted);
  font-variant-numeric: tabular-nums;
}

.display-1,
.display-2,
.display-3 {
  font-family: var(--font-sans);
  font-weight: var(--weight-extrabold);
  line-height: var(--leading-display);
  letter-spacing: var(--tracking-display-xl);
  color: var(--page-fg);
  text-wrap: balance;
}

.display-1 { font-size: var(--fs-display-1); }
.display-2 { font-size: var(--fs-display-2); }
.display-3 { font-size: var(--fs-display-3); line-height: 1.0; }

/* Vietnamese needs more leading — diacritics collide at 0.95. */
html[lang="vi"] .display-1,
html[lang="vi"] .display-2 { line-height: 1.04; }

html[lang="vi"] .display-3 { line-height: 1.08; }

.h1, .h2, .h3, .h4 {
  font-family: var(--font-sans);
  font-weight: var(--weight-bold);
  letter-spacing: var(--tracking-tight);
  line-height: var(--leading-snug);
  color: var(--page-fg);
  text-wrap: balance;
}

.h1 { font-size: var(--fs-h1); font-weight: var(--weight-extrabold); }
.h2 { font-size: var(--fs-h2); font-weight: var(--weight-extrabold); }
.h3 { font-size: var(--fs-h3); }
.h4 { font-size: var(--fs-h4); font-weight: var(--weight-semibold); }

.lead {
  font-size: var(--fs-lead);
  line-height: var(--leading-normal);
  color: var(--page-body);
}

.body { color: var(--page-body); }

.caption {
  font-size: var(--text-sm);
  line-height: var(--leading-normal);
  color: var(--page-muted);
}

/* Accent word inside a heading. Resolves to navy on light, yellow on navy —
   so it is never yellow-on-white. */
.hl { color: var(--page-accent-text); }

/* On light chapters an accent word gets a yellow underline instead of colour. */
[data-theme="light"] .hl {
  background-image: linear-gradient(var(--yellow-500), var(--yellow-500));
  background-repeat: no-repeat;
  background-position: 0 88%;
  background-size: 100% 0.28em;
  padding-inline: 0.04em;
}

.mono-num {
  font-family: var(--font-mono);
  font-weight: var(--weight-medium);
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.02em;
}

/* -- Buttons -------------------------------------------------------------- */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: var(--space-2);
  padding: 13px 22px;
  border-radius: var(--radius-md);
  font-family: var(--font-sans);
  font-size: var(--text-sm);
  font-weight: var(--weight-bold);
  letter-spacing: 0.01em;
  cursor: pointer;
  transition: background-color var(--dur-base) ease,
              color var(--dur-base) ease,
              border-color var(--dur-base) ease,
              transform var(--dur-base) ease,
              box-shadow var(--dur-base) ease;
}

.btn:hover { transform: translateY(-2px); }
.btn:active { transform: translateY(0); }

.btn-yellow {
  background: var(--yellow-500);
  color: var(--navy-900);
  box-shadow: var(--shadow-yellow);
}

.btn-yellow:hover { background: var(--yellow-700); }

.btn-solid {
  background: var(--page-fg);
  color: var(--page-bg);
}

.btn-outline {
  border: 1px solid var(--page-border);
  color: var(--page-fg);
}

.btn-outline:hover { border-color: var(--page-fg); }

.btn-sm { padding: 9px 16px; font-size: var(--text-xs); }
.btn-lg { padding: 16px 28px; font-size: var(--text-base); }

/* -- Reveal state --------------------------------------------------------- */

/* Only hide content once JS has confirmed it can animate it back in.
   No JS, or a JS error before .js-ready lands, means everything stays visible. */
.js-ready [data-reveal] {
  opacity: 0;
  will-change: transform, opacity;
}

.js-ready [data-reveal="up"] { transform: translate3d(0, 40px, 0); }

.js-ready [data-reveal-clip] {
  clip-path: inset(100% 0 0 0);
  will-change: clip-path;
}

/* -- Reduced motion ------------------------------------------------------- */

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }

  *,
  *::before,
  *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }

  /* Nothing may be left hidden behind an animation that will not run. */
  .js-ready [data-reveal],
  .js-ready [data-reveal-clip] {
    opacity: 1 !important;
    transform: none !important;
    clip-path: none !important;
    will-change: auto;
  }
}