:root {
  --accent: #1c4e8a;
  --accent-light: #eaf1fb;
  --path: #eb6834;
  --path-light: #fdf0ea;
  --grey: #8d8c87;
  --ink: #1a1a1a;
  --muted: #6b6a65;
  --line: #e2e1dc;
  --pale: #f6f5f1;
  --serif: "Computer Modern Serif", "Latin Modern Roman", Georgia, serif;
  --mono: "DejaVu Sans Mono", ui-monospace, monospace;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  color: var(--ink);
  background: #fff;
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.5;
}

header, main, footer { max-width: 1040px; margin: 0 auto; padding: 0 20px; }
header { padding-top: 40px; }
h1 { color: var(--accent); font-size: 32px; margin: 0 0 4px; font-weight: bold; }
h2 { color: var(--accent); font-size: 23px; margin: 0 0 6px; }
.byline { color: var(--muted); margin: 0 0 18px; }
section { padding: 34px 0 10px; border-top: 1px solid var(--line); }
section:first-child { border-top: none; }
.lead { margin: 0 0 16px; }
.num { color: var(--accent); }
.bad { color: var(--path); }
.change { color: var(--accent); margin: 0; font-size: 15px; }
.readout { font-family: var(--mono); font-size: 13px; min-height: 1.4em; margin: 4px 0 0; }
.legend { display: flex; flex-wrap: wrap; gap: 4px 14px; font-size: 13px; color: var(--muted); margin: 6px 0 0; }
.legend i { display: inline-block; width: 11px; height: 11px; margin-right: 5px; vertical-align: -1px; border-radius: 2px; }
.pair { display: grid; grid-template-columns: minmax(0, 620fr) minmax(0, 420fr); gap: 24px; align-items: start; }
.caption, .note { color: var(--muted); font-size: 15px; margin: 6px 0 14px; }
footer { color: var(--muted); font-size: 14px; padding: 30px 20px 50px; }
footer a, .byline a { color: var(--accent); }
code, .mono { font-family: var(--mono); font-size: 0.86em; }

#controls {
  position: sticky;
  top: 0;
  z-index: 5;
  display: flex;
  flex-wrap: wrap;
  gap: 18px 30px;
  align-items: center;
  max-width: 1040px;
  margin: 0 auto;
  padding: 10px 20px;
  background: rgba(255, 255, 255, 0.96);
  border-bottom: 1px solid var(--line);
}
.control { display: flex; flex-direction: column; gap: 4px; }
.label { color: var(--muted); font-size: 14px; }
#period-value { color: var(--ink); }
#period { width: 220px; accent-color: var(--accent); }

button {
  font: inherit;
  font-size: 15px;
  color: var(--ink);
  background: #fff;
  border: 1px solid #c9c8c2;
  border-radius: 4px;
  padding: 3px 10px;
  cursor: pointer;
}
button:hover { border-color: var(--accent); }
button.on { background: var(--accent); border-color: var(--accent); color: #fff; }
button.primary { background: var(--accent-light); border-color: var(--accent); color: var(--accent); }
button:disabled { opacity: 0.35; cursor: default; }

.segmented { display: flex; flex-wrap: wrap; gap: 4px; }
.corners { display: grid; grid-template-columns: 22px repeat(3, auto); gap: 3px 4px; align-items: center; font-size: 13px; }
.corners button { font-size: 13px; padding: 1px 7px; }
.corners span { color: var(--muted); font-size: 13px; text-align: right; padding-right: 2px; }
.corners button:disabled { background: #fff !important; }
.difficulty { grid-column: 2 / 5; display: flex; align-items: center; gap: 6px; margin-top: 2px; }
.difficulty span { font-size: 11px; padding: 0; }
.difficulty i { flex: 1; height: 5px; border-radius: 3px; border: 1px solid #e2ddd6; }

.pickers { display: flex; flex-wrap: wrap; gap: 14px 34px; margin: 0 0 12px; align-items: center; }
.picker { display: flex; align-items: center; gap: 8px; }
.picker > span { font-style: italic; }
.picker .value { min-width: 26px; color: var(--accent); font-style: normal; }
.bits { display: flex; gap: 3px; }
.bits button { width: 30px; padding: 2px 0; font-family: var(--mono); }
.picker .arrow { color: var(--muted); }

.chips { display: flex; flex-wrap: wrap; gap: 6px; margin: 0 0 12px; }
.chips .heading { color: var(--muted); font-size: 14px; width: 100%; }
.chips button { font-size: 14px; }

.split { display: grid; grid-template-columns: minmax(0, 1fr) 320px; gap: 26px; align-items: start; }
.side { display: flex; flex-direction: column; gap: 10px; }
.buttons { display: flex; gap: 8px; align-items: center; margin: 8px 0; }
#transition-time, #cycle-window { flex: 1; width: 100%; accent-color: var(--accent); }

canvas { width: 100%; height: auto; display: block; }
#grid { max-width: 300px; cursor: pointer; }
svg { width: 100%; height: auto; display: block; }

#build-steps { margin: 0; padding-left: 22px; font-size: 15px; }
#build-steps li { cursor: pointer; color: var(--muted); padding: 1px 0; }
#build-steps li.done { color: var(--ink); }
#build-steps li.current { color: var(--accent); font-weight: bold; }

.progress { height: 3px; background: var(--line); margin: 0 0 12px; visibility: hidden; }
.progress div { height: 100%; width: 0; background: var(--accent); }

table { border-collapse: collapse; font-size: 15px; margin: 18px 0 0; }
th, td { border-bottom: 1px solid var(--line); padding: 4px 14px; text-align: right; }
th:first-child, td:first-child { text-align: left; }
th { color: var(--muted); font-weight: normal; }
td.fail { color: var(--path); }
td.current { background: var(--accent-light); }

@media (max-width: 820px) {
  .split, .pair { grid-template-columns: 1fr; }
  #controls { position: static; }
  /* Wide figures scroll sideways instead of shrinking their text below reading size. */
  #array, #wave, #cycle-wave { min-width: 640px; }
  section { overflow-x: auto; }
}