/* Neural net digit reader project site */

/* Colours are taken from the dataset and from handwriting: the black background
   and white strokes of the MNIST digits, and the blue of ballpoint ink. */

:root {
  --bg: #f4f6fb;
  --surface: #ffffff;
  --text: #0e1430;
  --muted: #4e5674;
  --border: #d6dbea;
  --accent: #2446c7;
  --accent-text: #ffffff;
  --code-bg: #e6eaf5;
  --paper: #000000;
  --stroke: #ffffff;
  --signal: #0e1430;
  --right: #1d8a4c;
  --wrong: #c93838;
  --hero-from: #22348f;
  --hero-to: #0b1030;
  --hero-text: #ffffff;
  --hero-muted: #d3dafa;
  --max: 64rem;
  --gutter: 1rem;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0a0d1a;
    --surface: #111632;
    --text: #e6e9f6;
    --muted: #9aa3c4;
    --border: #232b52;
    --accent: #8aa4ff;
    --accent-text: #0a0d1a;
    --code-bg: #161c3d;
    --signal: #ffffff;
    --right: #4fd18b;
    --wrong: #ff7070;
    --hero-from: #1a2670;
    --hero-to: #070a1c;
    --hero-text: #f2f4fd;
    --hero-muted: #bcc6ee;
  }
}

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

html { scroll-behavior: smooth; scroll-padding-top: 4rem; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 1rem/1.6 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

.wrap {
  max-width: var(--max);
  margin: 0 auto;
  padding: 0 var(--gutter);
}

a { color: var(--accent); }

code, pre {
  font-family: ui-monospace, "SFMono-Regular", Menlo, Consolas, monospace;
  font-size: 0.9em;
}
code { background: var(--code-bg); padding: 0.1em 0.3em; border-radius: 3px; }
pre {
  background: var(--code-bg);
  padding: 1rem;
  border-radius: 6px;
  overflow-x: auto;
}
pre code { background: none; padding: 0; }

/* Header */

.site-header {
  position: sticky;
  top: 0;
  z-index: 10;
  background: var(--surface);
  border-bottom: 1px solid var(--border);
}
.site-header .wrap {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 1.5rem;
  padding-top: 0.75rem;
  padding-bottom: 0.75rem;
}
.brand { font-weight: 700; color: var(--text); text-decoration: none; }
/* A single square pixel */
.brand::before {
  content: "";
  display: inline-block;
  width: 0.6em;
  height: 0.6em;
  margin-right: 0.45em;
  border-radius: 1px;
  background: var(--accent);
  vertical-align: 0.05em;
}
.site-header nav { display: flex; flex-wrap: wrap; gap: 0.25rem 1rem; }
.site-header nav a { color: var(--muted); text-decoration: none; font-size: 0.95rem; }
.site-header nav a:hover { color: var(--text); }

/* Sections */

section { padding: 3rem 0; border-bottom: 1px solid var(--border); }
section:last-of-type { border-bottom: none; }

h1 { font-size: clamp(1.8rem, 5vw, 2.8rem); line-height: 1.15; margin: 0.25rem 0 1rem; }
h2 { font-size: 1.6rem; margin: 0 0 1rem; }
h3 { font-size: 1.15rem; margin: 2rem 0 0.75rem; }
h4 { font-size: 1rem; margin: 1.5rem 0 0.5rem; color: var(--muted); }

.eyebrow {
  margin: 0;
  color: var(--muted);
  font-size: 0.85rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
}
.lede { font-size: 1.15rem; color: var(--muted); max-width: 44rem; }

/* Hero: ink blue fading to the black of the dataset's images */

.hero {
  background: linear-gradient(160deg, var(--hero-from), var(--hero-to));
  color: var(--hero-text);
  border-bottom: none;
}
.hero .eyebrow,
.hero .lede { color: var(--hero-muted); }
.hero .button { background: var(--hero-text); color: var(--hero-to); }
.hero .button.secondary {
  background: transparent;
  color: var(--hero-text);
  border-color: var(--hero-text);
}
.hero .screenshot figcaption { color: var(--hero-muted); }
.hero .screenshot img { border-color: rgba(255, 255, 255, 0.2); }

/* Text beside the sample of digits on wide screens */
.hero-layout { display: grid; gap: 0 2.5rem; align-items: center; }
.hero-layout .screenshot { max-width: 24rem; }
@media (min-width: 52rem) {
  .hero-layout { grid-template-columns: minmax(0, 1fr) 22rem; }
  .hero-layout .screenshot { margin: 0; }
}

.actions { display: flex; flex-wrap: wrap; gap: 0.75rem; margin: 1.5rem 0; }
.button {
  display: inline-block;
  padding: 0.6rem 1rem;
  border-radius: 6px;
  background: var(--accent);
  color: var(--accent-text);
  text-decoration: none;
  font-weight: 600;
  border: 1px solid transparent;
}
.button.secondary {
  background: transparent;
  color: var(--accent);
  border: 1px solid var(--accent);
}

/* Step cards */

.cards {
  list-style: none;
  counter-reset: card;
  padding: 0;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(13rem, 1fr));
  gap: 1rem;
}
.cards li {
  counter-increment: card;
  background: var(--surface);
  border: 1px solid var(--border);
  border-top: 3px solid var(--accent);
  border-radius: 8px;
  padding: 1rem;
}
.cards li strong { display: block; margin-bottom: 0.25rem; }
.cards li strong::before { content: counter(card) ". "; color: var(--muted); }

/* Key facts, and the glossary of terms */

.facts {
  display: grid;
  grid-template-columns: max-content 1fr;
  gap: 0.4rem 1.5rem;
}
.facts dt { font-weight: 600; }
.facts dd { margin: 0; color: var(--muted); }

@media (max-width: 30rem) {
  .facts { grid-template-columns: 1fr; }
  .facts dd { margin-bottom: 0.5rem; }
}

/* An aside that explains an idea in everyday terms */

.analogy {
  margin: 1.5rem 0;
  padding: 1rem 1.25rem;
  background: var(--surface);
  border: 1px solid var(--border);
  border-left: 3px solid var(--accent);
  border-radius: 8px;
}
.analogy p { margin: 0; }
.analogy p + p { margin-top: 0.5rem; }

/* Headline results */

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
  gap: 1rem;
  margin: 1.5rem 0;
}
.stat {
  margin: 0;
  background: var(--surface);
  border: 1px solid var(--border);
  border-top-width: 3px;
  border-radius: 8px;
  padding: 1.25rem;
}
.stat .value {
  display: block;
  font-size: 2.6rem;
  font-weight: 700;
  line-height: 1.1;
  font-variant-numeric: tabular-nums;
}
.stat .label { display: block; margin-top: 0.25rem; color: var(--muted); }
.stat.primary { border-top-color: var(--accent); }

/* Tables */

.table-scroll { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; background: var(--surface); }
th, td { text-align: left; padding: 0.5rem 0.75rem; border: 1px solid var(--border); vertical-align: top; }
th { background: var(--code-bg); }

/* Screenshots */

.screenshot { margin: 1.5rem 0; }
.screenshot img {
  display: block;
  width: 100%;
  max-width: 1024px;
  height: auto;
  border: 1px solid var(--border);
  border-radius: 8px;
}
.screenshot figcaption { margin-top: 0.5rem; color: var(--muted); font-size: 0.9rem; }

/* Images that are small to begin with are not blown up past their own size */
.screenshot.natural img { width: auto; max-width: 100%; }

/* Side by side, each figure grows in proportion to its image's aspect ratio
   (--ar, set on the figure) so both images come out the same height */
.screenshot-pair { display: grid; gap: 0 1.5rem; }
@media (min-width: 52rem) {
  .screenshot-pair { display: flex; align-items: flex-start; }
  .screenshot-pair > .screenshot { flex: var(--ar, 1) 1 0; min-width: 0; }
}

/* Diagrams: inline SVG, coloured from the theme tokens */

.diagram { margin: 1.5rem 0; }
.diagram-scroll { overflow-x: auto; }
.diagram svg { display: block; width: 100%; min-width: 720px; height: auto; }
.diagram figcaption { margin-top: 0.5rem; color: var(--muted); font-size: 0.9rem; }

.diagram text { fill: var(--text); font-size: 13px; }
.diagram .d-title { font-size: 15px; font-weight: 700; }
.diagram .d-head { font-size: 14px; font-weight: 600; }
.diagram .d-small { font-size: 12px; }
.diagram .d-muted { fill: var(--muted); font-weight: 400; }
.diagram .d-dots { font-size: 22px; fill: var(--muted); }

.diagram .d-box { fill: var(--surface); stroke: var(--border); stroke-width: 1.5; }
.diagram .d-flow { stroke: var(--accent); stroke-width: 2; fill: none; }
.diagram .d-arrowhead { fill: var(--accent); }

/* The digit, drawn as it is stored: white strokes on black */
.diagram .d-paper { fill: var(--paper); }
.diagram .d-ink { fill: var(--stroke); }

/* Each connection sets its own width and opacity for the strength of its signal.
   White lines on the dark theme; dark ink on the light one, where white wouldn't show. */
.diagram .d-wire { stroke: var(--signal); stroke-linecap: round; }
.diagram .d-node { fill: var(--surface); stroke: var(--muted); stroke-width: 1.5; }
.diagram .d-node-top { fill: var(--accent); stroke: var(--accent); }
/* The sigmoid curve inside each hidden unit */
.diagram .d-sigmoid { fill: none; stroke: var(--accent); stroke-width: 1.75; stroke-linecap: round; }
.diagram .d-on-accent { fill: var(--accent-text); }
.diagram .d-bar { fill: var(--muted); }
.diagram .d-bar-top { fill: var(--accent); }

/* Footer */

.site-footer { padding: 2rem 0; color: var(--muted); font-size: 0.9rem; }