/* How to Learn Free-Wheel Unicycle
   Signature: film-roll (rails + inverted gate) over slow plasma;
   text scrolls on top — no card. Lora + Barlow. */

:root {
  --void: #05060a;
  --film: #3a404c;
  /*
    Gate ≈ inverted plasma under a warm paper wash (same mix as .quest-link).
    Bright CMYK fills stay for solid chrome; *-ink tokens are WCAG AA on the gate.
  */
  --ink: #0a0c10;              /* ≥14:1 on gate */
  --ink-muted: #2f3a48;        /* ≥8:1 on gate */
  --process-y: #e8b400;        /* fill / chrome on dark or as solid chip */
  --process-y-ink: #6b5000;    /* yellow text on gate ≈7.5:1 vs white */
  --process-c: #7ec8f2;        /* light blue chrome on dark */
  --process-c-ink: #046078;    /* link / cyan text on gate ≈7.1:1 vs white */
  --head: var(--process-y-ink);
  --focus: var(--process-c-ink);
  --baseline: 1.65;
  --space-block: 2.75rem;
  --space-head-before: 3.25rem;
  --space-head-after: 1.35rem;
  --sprocket: 2.85rem;
  --measure: min(40rem, calc(100vw - 2 * var(--sprocket) - 1.5rem));
  --punch-h: 1.55rem;
  --punch-gap: 1.35rem;
  --serif: "Lora", "Iowan Old Style", "Palatino Linotype", Palatino, serif;
  --sans: "Barlow", "Avenir Next", "Segoe UI", sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, monospace;
}

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

html {
  scroll-behavior: smooth;
  background: var(--void);
}

body.fw-howto {
  margin: 0;
  min-height: 100vh;
  color: var(--ink);
  font-family: var(--serif);
  font-size: clamp(1.05rem, 0.95rem + 0.35vw, 1.2rem);
  line-height: var(--baseline);
  background: var(--void);
}

.page {
  position: relative;
  z-index: 1;
  min-height: 100vh;
  padding-bottom: 2.5rem;
  display: flow-root; /* keep film layer over bottom padding; no margin collapse */
}

.skip-link {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--process-y);
  color: var(--ink);
  padding: 0.65rem 0.85rem;
  z-index: 100;
  font-family: var(--sans);
  font-weight: 600;
  text-decoration: none;
}
.skip-link:focus,
.skip-link:focus-visible {
  left: 0.75rem;
  top: 0.75rem;
  position: fixed;
  outline: 3px solid var(--ink);
  outline-offset: 2px;
}

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

#orbit-canvas {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 0;
}

/* Film roll: full page height, scrolls with text */
.film-layer {
  position: absolute;
  inset: 0;
  z-index: 0;
  pointer-events: none;
}

.film-strip {
  position: absolute;
  top: 0;
  bottom: 0;
  left: 0;
  right: 0;
  width: min(calc(var(--measure) + 2 * var(--sprocket)), 100%);
  margin-inline: auto;
}

.film-gate {
  position: absolute;
  top: 0;
  bottom: 0;
  left: var(--sprocket);
  right: var(--sprocket);
  background: transparent;
  -webkit-backdrop-filter: invert(1) brightness(0.48) contrast(1.05) saturate(1.05);
  backdrop-filter: invert(1) brightness(0.48) contrast(1.05) saturate(1.05);
}
/* Warm paper wash — same luminance as .quest-link, plasma only a faint grain. */
.film-gate::after {
  content: "";
  position: absolute;
  inset: 0;
  background: color-mix(in srgb, var(--process-y) 22%, white);
  opacity: 0.9;
  pointer-events: none;
}

.film-rail {
  position: absolute;
  top: 0;
  bottom: 0;
  width: var(--sprocket);
  margin: 0;
  padding: 0;
  background: var(--film);
  /* Solid rail minus punch shapes = true transparent holes to field */
  -webkit-mask-image:
    linear-gradient(#000 0 0),
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 40 52'%3E%3Crect x='7' y='8' width='26' height='24' rx='5.5' fill='%23000'/%3E%3C/svg%3E");
  -webkit-mask-size: 100% 100%, 100% calc(var(--punch-h) + var(--punch-gap));
  -webkit-mask-repeat: no-repeat, repeat-y;
  -webkit-mask-position: 0 0, center top;
  -webkit-mask-composite: destination-out;
  mask-image:
    linear-gradient(#000 0 0),
    url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 40 52'%3E%3Crect x='7' y='8' width='26' height='24' rx='5.5' fill='%23000'/%3E%3C/svg%3E");
  mask-size: 100% 100%, 100% calc(var(--punch-h) + var(--punch-gap));
  mask-repeat: no-repeat, repeat-y;
  mask-position: 0 0, center top;
  mask-composite: subtract;
}
.film-rail--left { left: 0; }
.film-rail--right {
  right: 0;
  background: var(--film);
}

.site-top {
  position: relative;
  z-index: 2;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 1rem;
  width: var(--measure);
  max-width: 100%;
  margin: 0 auto;
  padding: 0.85rem 0.75rem;
  color: var(--ink);
  font-family: var(--sans);
  font-size: 0.85rem;
  letter-spacing: 0.04em;
}
.site-top a {
  color: inherit;
  text-decoration: underline;
  text-decoration-color: transparent;
  text-underline-offset: 0.18em;
  border-bottom: none;
}
.site-top a:hover,
.site-top a:focus-visible {
  color: var(--process-c-ink);
  text-decoration-color: var(--process-c-ink);
  outline: 2px solid var(--focus);
  outline-offset: 3px;
}
.site-top a[aria-current="page"] {
  color: var(--process-y-ink);
  text-decoration-color: var(--process-y-ink);
}

/* Copy over film — no card */
main.article {
  position: relative;
  z-index: 2;
  width: var(--measure);
  max-width: 100%;
  margin: 0 auto;
  padding: 1.75rem 0.75rem 0;
  background: transparent;
  border: none;
  box-shadow: none;
}

.orbit-mark {
  display: block;
  width: 2.75rem;
  height: 2.75rem;
  margin: 0 auto 1.75rem;
  border: 1.5px solid var(--process-y-ink);
  border-radius: 50%;
  position: relative;
}
.orbit-mark::before {
  content: "";
  position: absolute;
  inset: 22%;
  border: 1px solid color-mix(in srgb, var(--process-y-ink) 40%, transparent);
  border-radius: 50%;
}
.orbit-mark::after {
  content: "";
  position: absolute;
  width: 0.35rem;
  height: 0.35rem;
  border-radius: 50%;
  background: var(--process-c-ink);
  top: 8%;
  left: 50%;
  transform: translateX(-50%);
}

h1 {
  font-family: var(--sans);
  font-weight: 700;
  font-size: clamp(2.15rem, 1.7rem + 2vw, 3.1rem);
  line-height: 1.12;
  letter-spacing: -0.025em;
  text-align: center;
  text-wrap: balance;
  margin: 0 0 1.1rem;
  color: var(--process-y-ink);
}

.page-lede {
  text-align: center;
  color: var(--ink-muted);
  font-size: 1.08em;
  margin: 0 0 1.15rem;
  text-wrap: pretty;
}

.page-meta {
  text-align: center;
  font-family: var(--sans);
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  color: var(--ink-muted);
  margin: 0 0 var(--space-block);
  padding-bottom: 0;
  border-bottom: none;
}
.page-meta a {
  color: var(--process-c-ink);
  text-decoration: underline;
  text-underline-offset: 0.18em;
}
.page-meta a:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

main.article p {
  margin: 0 0 1.25em;
  text-align: justify;
  hyphens: auto;
  text-wrap: pretty;
  orphans: 3;
  widows: 3;
  color: var(--ink);
}

main.article h2 {
  font-family: var(--sans);
  font-weight: 700;
  font-size: clamp(1.35rem, 1.15rem + 0.7vw, 1.65rem);
  letter-spacing: -0.01em;
  line-height: 1.25;
  margin: var(--space-head-before) 0 var(--space-head-after);
  padding-top: 0;
  border-top: none;
  color: var(--process-y-ink);
}

.ladder-item {
  margin: 0 0 1.55rem;
  padding-left: 0.15rem;
}
.ladder-item h3 {
  font-family: var(--sans);
  font-weight: 600;
  font-size: 1.05em;
  line-height: 1.35;
  margin: 0 0 0.4rem;
  color: var(--process-y-ink);
}
.ladder-item p { margin: 0; }

.grade-table {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.92em;
  margin: 1.25rem 0 1.75rem;
  font-family: var(--sans);
}
.grade-table th,
.grade-table td {
  border-bottom: 1px solid rgba(20, 24, 31, 0.16);
  padding: 0.55rem 0.4rem;
  text-align: left;
  vertical-align: top;
  color: var(--ink);
}
.grade-table th {
  font-size: 0.72rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-muted);
  font-weight: 600;
}
.grade-table td:first-child {
  white-space: nowrap;
  color: var(--process-y-ink);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}

.refs {
  list-style: none;
  padding: 0;
  margin: 0.85rem 0 0;
  font-size: 0.92em;
}
.refs li {
  margin: 0 0 0.65rem;
  padding-left: 0.9rem;
  position: relative;
}
.refs li::before {
  content: "◦";
  position: absolute;
  left: 0;
  color: var(--process-y-ink);
}
.refs a {
  color: var(--process-c-ink);
  text-decoration: underline;
  text-underline-offset: 0.18em;
}
.refs a:focus-visible {
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}

.quest-link {
  display: block;
  margin: 2.25rem 0 0.75rem;
  padding: 1.1rem 1.15rem;
  border: 1px solid color-mix(in srgb, var(--process-y-ink) 28%, transparent);
  background: transparent;
  font-family: var(--sans);
  font-size: 0.95rem;
  text-decoration: underline;
  text-decoration-color: transparent;
  text-underline-offset: 0.18em;
  color: var(--ink);
}
.quest-link:hover,
.quest-link:focus-visible {
  text-decoration-color: var(--process-c-ink);
  outline: 2px solid var(--focus);
  outline-offset: 2px;
}
.quest-link span {
  display: block;
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-muted);
  margin-bottom: 0.2rem;
}

@media (max-width: 640px) {
  :root {
    --sprocket: 1.85rem;
    --punch-h: 1.15rem;
    --punch-gap: 1rem;
    --space-head-before: 2.5rem;
    --space-head-after: 1.1rem;
  }
  main.article {
    padding: 1.25rem 0.5rem 0;
  }
  main.article p { text-align: left; }
  .grade-table { font-size: 0.85em; }
}

@media (prefers-reduced-transparency: reduce) {
  .film-gate {
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
    background: #d8dee8;
  }
  .film-gate::after { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .film-gate {
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
    background: #c8d0dc;
  }
  .film-gate::after { display: none; }
}

@media (prefers-contrast: high) {
  :root {
    --ink: #000;
    --ink-muted: #1a1a1a;
    --process-y: #c90;
    --process-y-ink: #5a4500;
    --process-c: #08c;
    --process-c-ink: #004d66;
    --focus: #004d66;
  }
  .film-gate {
    -webkit-backdrop-filter: none;
    backdrop-filter: none;
    background: #e8eef4;
  }
  .film-gate::after { display: none; }
}