/* BitBraid's website. One typeface (Outfit, the wordmark's), the brand's
   three lane colours (brand/), dark or light as the
   visitor's system prefers. */

@font-face {
  font-family: "Outfit";
  src: url("fonts/Outfit-Variable.woff2") format("woff2");
  font-weight: 100 900;
  font-display: swap;
}

:root {
  color-scheme: dark;
  --bg: #0d131a;
  --raised: #141c25;
  --line: #223040;
  --text: #eef3f8;
  --muted: #8f9cad;
  --sky: #62a8f5;
  --orchid: #a98bf7;
  --amber: #ffb83d;
  --on-sky: #0d131a;
  --glow: 0.7;
  --shadow: 0 2.5rem 6rem -1.5rem rgb(0 0 0 / 0.7);

  --page: 76rem;
  --gutter: clamp(1.25rem, 4vw, 3rem);
  --measure: 40rem;
}

@media (prefers-color-scheme: light) {
  :root {
    color-scheme: light;
    --bg: #f6f8fb;
    --raised: #ffffff;
    --line: #dbe2ea;
    --text: #1d2733;
    --muted: #586676;
    --sky: #2f7bc8;
    --orchid: #7c5fd6;
    --amber: #f2a318;
    --on-sky: #ffffff;
    --glow: 0.4;
    --shadow: 0 2rem 5rem -1.5rem rgb(29 39 51 / 0.35);
  }
}

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

html {
  -webkit-text-size-adjust: 100%;
  text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Outfit", ui-sans-serif, system-ui, sans-serif;
  font-size: 1.125rem;
  font-weight: 380;
  line-height: 1.6;
  font-kerning: normal;
}

img {
  display: block;
  max-width: 100%;
  height: auto;
}

a {
  color: var(--sky);
  text-underline-offset: 0.18em;
  text-decoration-thickness: 1px;
}

a:hover {
  text-decoration-thickness: 2px;
}

:focus-visible {
  outline: 2px solid var(--sky);
  outline-offset: 3px;
  border-radius: 4px;
}

h1,
h2,
h3 {
  margin: 0;
  font-weight: 560;
  line-height: 1.15;
  text-wrap: balance;
}

p {
  margin: 0;
}

.skip {
  position: absolute;
  left: var(--gutter);
  top: -3rem;
  padding: 0.5rem 0.9rem;
  background: var(--raised);
  border-radius: 6px;
  z-index: 2;
}

.skip:focus {
  top: 1rem;
}

/* Header ---------------------------------------------------------------- */

.top {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  justify-content: space-between;
  gap: 0.75rem 2rem;
  max-width: var(--page);
  margin: 0 auto;
  padding: 1.25rem var(--gutter) 0;
}

.home img {
  width: 2.25rem;
  height: 2.25rem;
}

.top nav {
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem 1.75rem;
  font-size: 1rem;
}

.top nav a {
  color: var(--muted);
  text-decoration: none;
}

.top nav a:hover {
  color: var(--text);
}

@media (max-width: 30rem) {
  .top nav {
    gap: 0.25rem 1rem;
  }

  /* The section is at the foot of the page either way. */
  .top nav .wide-only {
    display: none;
  }
}

/* Hero ------------------------------------------------------------------ */

.hero {
  display: flex;
  flex-direction: column;
  align-items: center;
  max-width: var(--page);
  margin: 0 auto;
  padding: clamp(1.5rem, 5vw, 3.5rem) var(--gutter) clamp(2.5rem, 5vw, 3.5rem);
  text-align: center;
}

.hero h1 img {
  width: clamp(15rem, 34vw, 27.5rem);
}

.lede {
  max-width: var(--measure);
  margin-top: 0.25rem;
  font-size: clamp(1.15rem, 1rem + 0.5vw, 1.4rem);
  color: var(--muted);
}

.actions {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;
  gap: 1rem 1.75rem;
  margin-top: 2rem;
}

.button {
  display: inline-block;
  padding: 0.7rem 1.35rem;
  border: 1px solid var(--line);
  border-radius: 999px;
  color: var(--text);
  font-weight: 520;
  text-decoration: none;
  white-space: nowrap;
}

.button:hover {
  border-color: var(--sky);
}

.button.primary {
  background: var(--sky);
  border-color: var(--sky);
  color: var(--on-sky);
}

.button.primary:hover {
  filter: brightness(1.08);
}

.quiet {
  color: var(--text);
}

/* The screenshot, threaded on the braid ---------------------------------- */

.stage {
  /* The braid is as wide as the window; nothing scrolls sideways. */
  overflow-x: clip;
  padding-bottom: 1rem;
}

.shot {
  position: relative;
  max-width: calc(64rem + 2 * var(--gutter));
  margin: 0 auto;
  padding: 0 var(--gutter);
}

.shot picture {
  position: relative;
  z-index: 1;
}

.shot img {
  width: 100%;
  /* Opaque while it loads, so the braid never shows through. */
  background: var(--raised);
  border: 1px solid var(--line);
  border-radius: 0.75rem;
  box-shadow: var(--shadow);
}

.braid {
  position: absolute;
  top: 24%;
  left: 50%;
  width: 100vw;
  margin-left: -50vw;
  translate: 0 -50%;
  opacity: 0;
  pointer-events: none;
}

.braid.is-drawn {
  opacity: 1;
  transition: opacity 1.4s ease-out;
}

.braid svg {
  position: absolute;
  top: 0;
  left: 50%;
  display: block;
  overflow: visible;
  animation: flow 9s linear infinite;
}

.braid.is-still svg {
  animation-play-state: paused;
}

.braid .glow {
  opacity: var(--glow);
}

.braid path {
  fill: none;
  stroke-linecap: butt;
  stroke-linejoin: round;
}

@keyframes flow {
  to {
    transform: translateX(var(--period));
  }
}

@media (prefers-reduced-motion: reduce) {
  .braid svg {
    animation: none;
  }

  .braid.is-drawn {
    transition: none;
  }
}

/* Sections: a heading on the left, the matter on the right -------------- */

.band {
  display: grid;
  grid-template-columns: minmax(0, 1fr);
  gap: 1.75rem;
  max-width: var(--page);
  margin: 0 auto;
  padding: clamp(4rem, 10vw, 7rem) var(--gutter) 0;
}

.band h2 {
  font-size: clamp(1.9rem, 1.4rem + 1.6vw, 2.5rem);
  letter-spacing: -0.015em;
}

@media (min-width: 60rem) {
  .band {
    grid-template-columns: 19rem minmax(0, 1fr);
    gap: 4rem;
  }

  .band h2 {
    position: sticky;
    top: 2rem;
    align-self: start;
  }
}

/* Features, drawn as a commit graph -------------------------------------- */

.graph {
  --lane-width: 3.75rem; /* 60 units of each row's picture */
  --node: 0.9rem;
  --node-at: 1.95rem; /* the middle of a heading's first line */
  max-width: 44rem;
  margin: 0;
  padding: 0;
  list-style: none;
}

.graph li {
  position: relative;
  padding: 0.95rem 0 1.4rem var(--lane-width);
}

.graph .lanes {
  position: absolute;
  inset: 0 auto 0 0;
  width: var(--lane-width);
  height: 100%;
  overflow: visible;
}

/* The first lane begins at the first commit, not above it. */
.graph li:first-child .lanes {
  top: var(--node-at);
  height: calc(100% - var(--node-at));
}

.graph .lanes path {
  fill: none;
  stroke-width: 2.5;
  stroke-linecap: round;
  vector-effect: non-scaling-stroke;
}

.l0 {
  --lane: var(--sky);
  --x: 14;
  stroke: var(--sky);
}

.l1 {
  --lane: var(--orchid);
  --x: 30;
  stroke: var(--orchid);
}

.l2 {
  --lane: var(--amber);
  --x: 46;
  stroke: var(--amber);
}

.graph .node {
  position: absolute;
  left: calc(var(--lane-width) * var(--x) / 60 - var(--node) / 2);
  top: calc(var(--node-at) - var(--node) / 2);
  width: var(--node);
  height: var(--node);
  border: 3px solid var(--lane);
  border-radius: 50%;
  background: var(--bg);
}

.graph h3 {
  font-size: 1.3rem;
  line-height: 1.5;
}

.graph p {
  margin-top: 0.25rem;
  color: var(--muted);
}

/* Download -------------------------------------------------------------- */

.downloads {
  max-width: 44rem;
}

.system {
  display: grid;
  grid-template-columns: 7rem minmax(0, 1fr) auto;
  gap: 0.5rem 1.5rem;
  align-items: baseline;
  padding: 1.25rem 0;
  border-top: 1px solid var(--line);
}

.system:first-child {
  border-top: 0;
  padding-top: 0.4rem;
}

.system h3 {
  font-size: 1.3rem;
}

.system p {
  color: var(--muted);
}

.system.yours .button {
  background: var(--sky);
  border-color: var(--sky);
  color: var(--on-sky);
}

@media (max-width: 40rem) {
  .system {
    grid-template-columns: minmax(0, 1fr);
  }

  .system .button {
    justify-self: start;
    margin-top: 0.4rem;
  }
}

.source {
  margin-top: 1.25rem;
  padding: 1.5rem;
  background: var(--raised);
  border: 1px solid var(--line);
  border-radius: 0.75rem;
}

.source h3 {
  font-size: 1.15rem;
}

.source p {
  margin-top: 0.3rem;
  color: var(--muted);
  font-size: 1rem;
}

.source pre {
  margin: 1rem 0 0;
  overflow-x: auto;
  font-family: ui-monospace, "SF Mono", "Cascadia Mono", "JetBrains Mono", Menlo, Consolas, monospace;
  font-size: 0.9rem;
  line-height: 1.7;
}

/* How it was made: a note, smaller than the rest ------------------------ */

.band.note h2 {
  font-size: 1.3rem;
  letter-spacing: 0;
}

.prose {
  max-width: var(--measure);
  font-size: 1rem;
  color: var(--muted);
}

.prose p + p {
  margin-top: 0.85rem;
}

/* Footer ---------------------------------------------------------------- */

.bottom {
  width: min(var(--page) - 2 * var(--gutter), 100% - 2 * var(--gutter));
  margin: clamp(4rem, 10vw, 7rem) auto 0;
  padding: 2rem 0 3rem;
  border-top: 1px solid var(--line);
  font-size: 0.875rem;
  color: var(--muted);
}

.bottom p {
  max-width: 46rem;
}

.bottom p + p {
  margin-top: 0.5rem;
}

.bottom a {
  color: inherit;
}

@media (prefers-reduced-motion: no-preference) {
  html {
    scroll-behavior: smooth;
  }
}