/* Teaching Lisp to Read
 * A long read with live Lisp cells in it. Serif for the prose, so it can be
 * read for half an hour without tiring; monospace for anything Lisp says. */

:root {
  --ink: #1b1b1b;
  --paper: #fdfcf9;
  --muted: #6a6a6a;
  --rule: #e3e0d8;
  --accent: #2a6f97;
  --ok: #2f7d4f;
  --bad: #a33a2e;
  --code-bg: #f4f2ec;
  --cell-border: #d9d5ca;
  --out-bg: #faf9f5;
  --serif: Georgia, "Iowan Old Style", "Palatino Linotype", Palatino, "Book Antiqua", "Times New Roman", serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", "Courier New", monospace;
}

@media (prefers-color-scheme: dark) {
  :root {
    --ink: #e4e2dc;
    --paper: #151515;
    --muted: #9a9890;
    --rule: #2c2c2c;
    --accent: #7cc4ea;
    --ok: #7bc99a;
    --bad: #e08a7e;
    --code-bg: #1e1e1e;
    --cell-border: #363636;
    --out-bg: #191919;
  }
}

* {
  box-sizing: border-box;
}

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

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 1.0625rem;
  line-height: 1.7;
}

a {
  color: var(--accent);
  text-decoration: underline;
  text-underline-offset: 0.15em;
}

a:hover {
  text-decoration-style: dotted;
}

.back_link {
  position: absolute;
  top: 1rem;
  left: 1.2rem;
  font-family: var(--mono);
  font-size: 0.8rem;
  letter-spacing: 0.1em;
  color: var(--muted);
  text-decoration: none;
}

.back_link:hover {
  color: var(--accent);
}

article {
  max-width: 40rem;
  margin: 0 auto;
  padding: 4.5rem 1rem 5rem;
}

/* ---- header ---- */

.kicker {
  font-family: var(--mono);
  font-size: 0.78rem;
  letter-spacing: 0.06em;
  color: var(--muted);
  margin: 0 0 1rem;
}

.kicker .made-by {
  display: inline-block;
  padding: 0 0.45em;
  border: 1px solid currentColor;
  border-radius: 3px;
  color: var(--accent);
  line-height: 1.5;
}

h1 {
  font-weight: normal;
  font-size: 2.3rem;
  line-height: 1.15;
  margin: 0 0 0.8rem;
  letter-spacing: -0.01em;
}

.subtitle {
  font-size: 1.15rem;
  color: var(--muted);
  margin: 0 0 1rem;
  line-height: 1.5;
}

.byline {
  font-family: var(--mono);
  font-size: 0.8rem;
  color: var(--muted);
  margin: 0 0 3rem;
  padding-bottom: 1.2rem;
  border-bottom: 1px solid var(--rule);
}

/* ---- prose ---- */

h2 {
  font-weight: normal;
  font-size: 1.65rem;
  line-height: 1.25;
  margin: 3.6rem 0 1.2rem;
}

h2 .part {
  display: block;
  font-family: var(--mono);
  font-size: 0.75rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  margin-bottom: 0.5rem;
}

h3 {
  font-weight: normal;
  font-size: 1.22rem;
  margin: 2.6rem 0 0.8rem;
}

p {
  margin: 0 0 1.15rem;
}

em {
  font-style: italic;
}

code {
  font-family: var(--mono);
  font-size: 0.86em;
  background: var(--code-bg);
  padding: 0.08em 0.32em;
  border-radius: 3px;
}

pre code {
  background: none;
  padding: 0;
  font-size: inherit;
}

blockquote {
  margin: 1.6rem 0;
  padding: 0 0 0 1.1rem;
  border-left: 2px solid var(--rule);
  color: var(--ink);
}

blockquote p {
  margin-bottom: 0.5rem;
}

blockquote cite {
  display: block;
  font-style: normal;
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--muted);
}

ul, ol {
  padding-left: 1.4rem;
}

li {
  margin-bottom: 0.4rem;
}

hr {
  border: 0;
  border-top: 1px solid var(--rule);
  margin: 3rem auto;
  width: 6rem;
}

.aside {
  font-size: 0.95rem;
  color: var(--muted);
  border-top: 1px solid var(--rule);
  border-bottom: 1px solid var(--rule);
  padding: 0.9rem 0;
  margin: 1.8rem 0;
}

.aside p:last-child {
  margin-bottom: 0;
}

/* ---- live Lisp cells ---- */

.cell {
  margin: 1.5rem 0 1.7rem;
  border: 1px solid var(--cell-border);
  border-radius: 6px;
  background: var(--code-bg);
  overflow: hidden;
}

.cell textarea {
  display: block;
  width: 100%;
  margin: 0;
  border: 0;
  background: transparent;
  color: var(--ink);
  font-family: var(--mono);
  font-size: 0.88rem;
  line-height: 1.55;
  padding: 0.85rem 1rem 0.7rem;
  resize: none;
  outline: none;
  tab-size: 2;
  overflow: hidden;
  white-space: pre;
  overflow-x: auto;
}

.cell:focus-within {
  border-color: var(--accent);
  box-shadow: 0 0 0 1px var(--accent);
}

.cell .bar {
  display: flex;
  align-items: center;
  gap: 0.9rem;
  padding: 0.35rem 0.6rem 0.35rem 1rem;
  border-top: 1px solid var(--cell-border);
  font-family: var(--mono);
  font-size: 0.74rem;
  color: var(--muted);
}

.cell .bar .hint {
  margin-left: auto;
}

button {
  font-family: var(--mono);
  font-size: 0.76rem;
  letter-spacing: 0.04em;
  color: var(--ink);
  background: var(--paper);
  border: 1px solid var(--cell-border);
  border-radius: 4px;
  padding: 0.3rem 0.8rem;
  cursor: pointer;
  transition: border-color 0.15s ease, color 0.15s ease;
}

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

button:disabled {
  opacity: 0.5;
  cursor: default;
}

.cell .output {
  margin: 0;
  padding: 0.7rem 1rem;
  border-top: 1px solid var(--cell-border);
  background: var(--out-bg);
  font-family: var(--mono);
  font-size: 0.88rem;
  line-height: 1.55;
  white-space: pre-wrap;
  word-break: break-word;
  max-height: 24rem;
  overflow: auto;
}

.cell .output:empty {
  display: none;
}

.cell .output .value {
  color: var(--accent);
}

.cell .output .error {
  color: var(--bad);
}

.cell .output .note {
  color: var(--muted);
}

.cell.running .bar {
  color: var(--accent);
}

/* ---- status pill ---- */

#lisp_status {
  position: fixed;
  right: 1rem;
  bottom: 1rem;
  z-index: 10;
  font-family: var(--mono);
  font-size: 0.72rem;
  letter-spacing: 0.04em;
  color: var(--muted);
  background: var(--paper);
  border: 1px solid var(--cell-border);
  border-radius: 999px;
  padding: 0.3rem 0.8rem;
  box-shadow: 0 2px 10px rgba(0, 0, 0, 0.08);
}

#lisp_status.ready { color: var(--ok); }
#lisp_status.failed { color: var(--bad); }

#lisp_status.quiet {
  opacity: 0.35;
  transition: opacity 1.5s ease;
}

#lisp_status.quiet:hover {
  opacity: 1;
}

/* ---- the digit demos ---- */

.panel {
  margin: 1.6rem 0 2rem;
  border: 1px solid var(--cell-border);
  border-radius: 6px;
  padding: 1rem 1.1rem;
  background: var(--out-bg);
  font-family: var(--mono);
  font-size: 0.82rem;
  color: var(--muted);
}

.panel h4 {
  margin: 0 0 0.8rem;
  font-weight: normal;
  font-size: 0.76rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
}

.panel .row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.6rem 0.9rem;
  margin-bottom: 0.7rem;
}

.panel .row:last-child {
  margin-bottom: 0;
}

.panel .readout {
  color: var(--ink);
}

.panel .readout b {
  font-weight: normal;
  color: var(--accent);
}

.digits {
  display: grid;
  grid-template-columns: repeat(10, minmax(0, 1fr));
  gap: 0.6rem 0.5rem;
}

#mistakes {
  grid-template-columns: repeat(6, minmax(0, 1fr));
}

.digit {
  text-align: center;
  line-height: 1.2;
}

.digit canvas {
  display: block;
  width: 100%;
  max-width: 56px;
  height: auto;
  aspect-ratio: 1 / 1;
  margin: 0 auto;
  image-rendering: pixelated;
  border-radius: 3px;
  background: #000;
}

.digit .label {
  display: block;
  margin-top: 0.25rem;
  font-size: 0.72rem;
  color: var(--muted);
}

.digit .label.right { color: var(--ok); }
.digit .label.wrong { color: var(--bad); }

canvas.spark {
  display: block;
  width: 100%;
  height: 80px;
  border-radius: 3px;
  background: var(--code-bg);
}

.panel .note,
.panel .caption {
  margin: 0.7rem 0 0;
  font-size: 0.78rem;
  line-height: 1.5;
  color: var(--muted);
}

.panel .note:empty {
  display: none;
}

/* the 64 hidden neurons, as pictures */

.neurons {
  display: grid;
  grid-template-columns: repeat(8, 1fr);
  gap: 4px;
  max-width: 420px;
}

.neurons canvas {
  display: block;
  width: 100%;
  height: auto;
  aspect-ratio: 1 / 1;
  image-rendering: pixelated;
  border-radius: 2px;
}

input[type="range"] {
  accent-color: var(--accent);
  width: 10rem;
}

/* draw pad */

.drawpad {
  display: grid;
  grid-template-columns: auto 1fr;
  gap: 1.2rem 1.6rem;
  align-items: start;
}

#pad {
  display: block;
  width: 252px;
  height: 252px;
  border-radius: 6px;
  background: #000;
  cursor: crosshair;
  touch-action: none;
  border: 1px solid var(--cell-border);
}

.pad_tools {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  margin-top: 0.6rem;
}

.sees {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1rem;
}

#seen {
  display: block;
  width: 84px;
  height: 84px;
  image-rendering: pixelated;
  border-radius: 3px;
  background: #000;
  border: 1px solid var(--cell-border);
}

.bars {
  display: grid;
  grid-template-columns: 1.4em 1fr 3.4em;
  gap: 0.25rem 0.6rem;
  align-items: center;
}

.bars .d {
  color: var(--ink);
  text-align: right;
}

.bars .track {
  height: 0.75rem;
  background: var(--code-bg);
  border-radius: 2px;
  overflow: hidden;
}

.bars .fill {
  height: 100%;
  width: 0;
  background: var(--accent);
  border-radius: 2px;
  transition: width 0.15s ease;
}

.bars .top .fill { background: var(--ok); }
.bars .pct { text-align: right; }

.verdict {
  font-family: var(--serif);
  font-size: 1.3rem;
  color: var(--ink);
  margin: 0 0 0.8rem;
  min-height: 1.6em;
}

@media (hover: none) {
  .cell .bar .hint {
    display: none;
  }
}

@media (max-width: 560px) {
  article {
    padding-top: 3.6rem;
  }

  .cell textarea,
  .cell .output {
    font-size: 0.8rem;
  }

  #lisp_status.quiet {
    opacity: 0;
    pointer-events: none;
  }

  h1 {
    font-size: 1.9rem;
  }

  .drawpad {
    grid-template-columns: 1fr;
  }

  #pad {
    width: 100%;
    max-width: 320px;
    height: auto;
    aspect-ratio: 1 / 1;
  }

  .digits {
    grid-template-columns: repeat(5, minmax(0, 1fr));
  }

  #mistakes {
    grid-template-columns: repeat(3, minmax(0, 1fr));
  }
}

/* ---- about box ---- */

.about {
  margin-top: 3.5rem;
  border-top: 1px solid var(--rule);
  padding-top: 1.4rem;
  font-size: 0.92rem;
  color: var(--muted);
}

.about h2 {
  font-size: 1.1rem;
  margin: 0 0 0.8rem;
  color: var(--ink);
}

.about p {
  margin-bottom: 0.7rem;
}