/* Chalk on an easel: paper for the page, ink for the figures, one hue per column. */
:root {
  --bg: #f7f4ee;
  --surface: #ffffff;
  --border: #ddd8cd;
  --text: #1c1b19;
  --muted: #6d6a62;
  --accent: #bf3b2f;
  --accent-soft: #fbe7e3;
  --ok: #1f7a58;
  --danger: #b5462f;
  --felt: #eaf1e9;
  --felt-edge: #cfe0d2;
  --board: #fdfcf8;
  --board-edge: #e3ddd0;
  --radius: 10px;
  --ord-ink: #ffffff;
  --warn: #9a6207;
  --warn-soft: #fbf0dc;
  --tint: 16%;          /* how strongly a column hue washes its cells */
  --tint-lit: 34%;
  color-scheme: light dark;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #14171a;
    --surface: #1f242a;
    --border: #333a42;
    --text: #edeff1;
    --muted: #9aa3ac;
    --accent: #ff7d6b;
    --accent-soft: #3a211d;
    --ok: #55c99b;
    --danger: #ff8566;
    --felt: #16241e;
    --felt-edge: #294036;
    --board: #191d22;
    --board-edge: #2d343b;
    --ord-ink: #1a1613;
    --warn: #f0b95e;
    --warn-soft: #33290f;
    --tint: 22%;
    --tint-lit: 45%;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  padding: 2rem 1rem 4rem;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.55 ui-sans-serif, -apple-system, "Segoe UI", Roboto, sans-serif;
}

header, main, footer { max-width: 60rem; margin: 0 auto; }
header { border-bottom: 2px solid var(--accent-soft); margin-bottom: 1.5rem; }

h1 { font-size: 1.7rem; margin: 0 0 .2rem; }
h1 .qualifier { font-weight: 400; color: var(--muted); }
h2 {
  font-size: 1.05rem;
  margin: 0 0 1rem;
  text-transform: uppercase;
  letter-spacing: .07em;
  color: var(--accent);
}
h3 { font-size: 1rem; margin: 1.2rem 0 .4rem; }

.tagline { margin: 0 0 .9rem; font-size: .95rem; color: var(--accent); }
.lede { color: var(--muted); margin: 0 0 1.25rem; }
.hint { font-size: .85rem; color: var(--muted); }
.hint a { color: var(--accent); }

.note {
  display: flex;
  gap: .7rem;
  align-items: flex-start;
  margin: 0 0 1.5rem;
  padding: .75rem .95rem;
  background: var(--accent-soft);
  border-left: 3px solid var(--accent);
  border-radius: 0 var(--radius) var(--radius) 0;
}
.note::before {
  content: "i";
  flex: none;
  width: 1.15rem;
  height: 1.15rem;
  margin-top: .12rem;
  display: grid;
  place-items: center;
  border-radius: 99px;
  background: var(--accent);
  color: var(--ord-ink);
  font: italic 700 .78rem/1 Georgia, "Times New Roman", serif;
}
.note p { margin: 0; font-size: .9rem; }
.note[hidden] { display: none; }

/* An explanation that stays folded until it is asked for. */
.more {
  margin-top: .9rem;
  padding: .6rem .95rem;
  border: 1px dashed var(--border);
  border-radius: var(--radius);
}
.more summary { cursor: pointer; font-size: .9rem; font-weight: 600; }
.more p { margin: .6rem 0 0; font-size: .87rem; color: var(--muted); }
.more code { font: 600 .85rem ui-monospace, Menlo, monospace; color: var(--text); white-space: nowrap; }

/* A worked example: same shape as the note, in the felt green. */
.example {
  display: flex;
  gap: .7rem;
  align-items: flex-start;
  margin: 0 0 1rem;
  padding: .75rem .95rem;
  background: var(--felt);
  border-left: 3px solid var(--ok);
  border-radius: 0 var(--radius) var(--radius) 0;
}
.example::before {
  content: "e.g.";
  flex: none;
  margin-top: .15rem;
  padding: .05rem .4rem;
  border-radius: 99px;
  background: var(--ok);
  color: var(--ord-ink);
  font-size: .62rem;
  font-weight: 700;
  letter-spacing: .04em;
}
.example p { margin: 0; font-size: .9rem; }

/* Where the method came from. */
.ack {
  display: block;
  margin: 0 0 1rem;
  padding: .7rem .95rem;
  border: 1px dashed var(--border);
  border-radius: var(--radius);
}
.ack h2 {
  font-size: .68rem;
  letter-spacing: .1em;
  text-transform: uppercase;
  color: var(--muted);
  margin: 0 0 .35rem;
}
.ack p { margin: 0 0 .5rem; font-size: .87rem; color: var(--muted); }
.ack p:last-child { margin-bottom: 0; }
.ack a { color: var(--accent); overflow-wrap: anywhere; }

.panel {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 1.25rem;
  margin-bottom: 1.25rem;
}

/* The step number that runs down the left of each stage. */
.stagehead { display: flex; align-items: baseline; gap: .7rem; flex-wrap: wrap; }
.stagehead h2 { margin-bottom: 1rem; }
.step {
  flex: none;
  width: 1.5rem;
  height: 1.5rem;
  display: grid;
  place-items: center;
  border-radius: 99px;
  background: var(--accent);
  color: var(--ord-ink);
  font-size: .8rem;
  font-weight: 700;
}
.stagehead .spacer { flex: 1 1 auto; }

button {
  font: inherit;
  font-size: .9rem;
  padding: .45rem .85rem;
  border-radius: 6px;
  border: 1px solid var(--border);
  background: var(--bg);
  color: var(--text);
  cursor: pointer;
}
button.primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #fff;
  font-weight: 600;
  box-shadow: 0 1px 3px rgba(191, 59, 47, .35);
}
button.primary:hover { filter: brightness(1.07); }
button:disabled { opacity: .45; cursor: default; box-shadow: none; }
button.ghost { font-size: .85rem; padding: .35rem .7rem; }

.controls {
  display: flex;
  align-items: center;
  gap: .5rem;
  flex-wrap: wrap;
  margin: 1rem 0 .25rem;
}
.controls .spacer { flex: 1 1 auto; }
/* ---- setup ---- */

.setup {
  display: grid;
  grid-template-columns: max-content minmax(0, 22rem) 1fr;
  gap: .55rem .85rem;
  align-items: center;
  margin-bottom: .9rem;
}
.setup label { font-size: .9rem; }
.setup input, .setup select, .setup textarea, .controls input {
  font: inherit;
  font-size: .95rem;
  padding: .35rem .5rem;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
  min-width: 0;
}
.setup .aside { font-size: .8rem; color: var(--muted); }
.setup textarea { resize: vertical; font-family: inherit; }
.setup input.short { width: 5rem; }
.setup [hidden] { display: none; }
.controls input.short { width: 4.5rem; }
.controls .inline { font-size: .9rem; }

.board {
  background: var(--board);
  border: 1px solid var(--board-edge);
  border-radius: var(--radius);
  padding: 1.1rem 1.2rem;
  overflow-x: auto;
}

/* ---- cards ---- */

.cardrow { display: flex; align-items: flex-start; gap: .8rem; margin-bottom: .9rem; }
.cardrow:last-child { margin-bottom: 0; }
.rowlabel {
  flex: none;
  width: 5.5rem;
  padding-top: .55rem;
  font-size: .75rem;
  color: var(--muted);
  letter-spacing: .03em;
}
.cards { display: flex; gap: .3rem; flex-wrap: wrap; }
.slot { display: flex; flex-direction: column; align-items: center; gap: .2rem; }
.sub { font: 400 .7rem/1 ui-sans-serif, sans-serif; color: var(--muted); }

.card {
  position: relative;
  display: grid;
  place-items: center;
  min-width: 2.3rem;
  padding: 0 .2rem;
  height: 3.1rem;
  border-radius: 6px;
  font: 700 1.1rem/1 ui-monospace, SFMono-Regular, Menlo, monospace;
  background: hsl(var(--h) 65% 50% / var(--tint));
  border: 1px solid hsl(var(--h) 55% 45% / .55);
  transition: transform .12s ease, background .12s ease;
}
.card.second::after {
  content: "";
  position: absolute;
  right: .22rem;
  bottom: .22rem;
  width: .35rem;
  height: .35rem;
  border-radius: 99px;
  background: hsl(var(--h) 55% 40%);
}
.card.lit { background: hsl(var(--h) 65% 50% / var(--tint-lit)); transform: translateY(-3px); }

/* ---- results ---- */

.reveal {
  margin: 1rem 0 0;
  padding: .8rem .95rem;
  background: var(--felt);
  border-left: 3px solid var(--ok);
  border-radius: 0 var(--radius) var(--radius) 0;
  font-size: .95rem;
}
.reveal strong { color: var(--ok); }
.reveal.waiting { background: var(--accent-soft); border-left-color: var(--accent); }
.reveal.waiting strong { color: var(--accent); }
.reveal.bad { background: var(--warn-soft); border-left-color: var(--danger); }
.reveal.bad strong { color: var(--danger); }

.suggest { display: flex; flex-wrap: wrap; gap: .4rem; align-items: center; margin: .8rem 0 .4rem; }
.suggest .hint { margin: 0; }

.facts { margin-top: .8rem; }
.fact { margin: 0 0 .4rem; font-size: .92rem; }
.fact.good { color: var(--ok); font-weight: 600; }
.fact.bad { color: var(--danger); font-weight: 600; }

.card.down {
  background: repeating-linear-gradient(135deg, hsl(var(--h) 65% 50% / var(--tint)) 0 6px, hsl(var(--h) 65% 50% / .05) 6px 12px);
  border-style: dashed;
}
.card.back { color: transparent; background: repeating-linear-gradient(135deg, var(--border) 0 6px, var(--bg) 6px 12px); border-color: var(--muted); }
.card.back::after { display: none; }

.words { display: flex; flex-wrap: wrap; gap: .5rem; margin-bottom: .5rem; }
.word { display: flex; flex-direction: column; gap: .15rem; padding: .35rem .6rem; border: 1px solid var(--border); border-radius: 8px; background: var(--bg); }
.word.now { border-color: var(--accent); box-shadow: 0 0 0 2px var(--accent-soft); }
.word.past { opacity: .55; }
.word .wm { font-size: .65rem; color: var(--muted); letter-spacing: .04em; }
.word .wtext { font: 600 1rem/1.2 ui-monospace, Menlo, monospace; letter-spacing: .08em; }
.let { color: var(--muted); }
.let.on { color: var(--accent); text-decoration: underline; }

table.rules { border-collapse: collapse; width: 100%; font-size: .9rem; }
.rules th { text-align: left; font-size: .72rem; color: var(--muted); font-weight: 600; padding: .2rem .6rem .4rem 0; }
.rules td { padding: .2rem .6rem .2rem 0; font-variant-numeric: tabular-nums; }
.rules tr.ok .mark { color: var(--ok); font-weight: 700; }
.rules tr.bad td { color: var(--danger); }
.rules tr.none td { color: var(--muted); }

#why p { margin: 0 0 .8rem; }
#why p:last-child { margin-bottom: 0; }
.factword { color: var(--ok); font-weight: 600; }

footer p { color: var(--muted); font-size: .85rem; }
footer a { color: var(--accent); }

/* The site masthead, as on the landing page. */
.sitebar {
  display: block;
  max-width: 60rem;
  margin: 0 auto 1.4rem;
  text-decoration: none;
  color: var(--text);
}
.sitebar-name { display: block; font-size: 1.25rem; font-weight: 700; margin: 0 0 .1rem; }
.sitebar-sub {
  display: block;
  font: italic 13px Georgia, "Times New Roman", serif;
  color: var(--muted);
  letter-spacing: 0;
}
.sitebar:hover .sitebar-name { color: var(--accent); }
.sitebar-horizon { display: block; width: 100%; height: auto; margin: .5rem 0 0; }
@media (prefers-color-scheme: dark) { .sitebar-horizon { filter: invert(1); } }

@media (max-width: 40rem) {
  .setup { grid-template-columns: 1fr; }
  .setup label { margin-bottom: -.35rem; }
  .card { width: 1.9rem; height: 2.7rem; font-size: 1rem; }
  .rowlabel { width: 4.2rem; }
}

/* Playing cards: white face, red or black pips, no hue wash. */
.card.pc { background: var(--surface); border: 1px solid var(--border); font-size: 1rem; }
.card.pc.red { color: #c0392b; }
@media (prefers-color-scheme: dark) { .card.pc.red { color: #ff7d6b; } }
.card.pc.black { color: var(--text); }
.card.pc.second::after { display: none; }
.card.pc.lit { background: var(--accent-soft); border-color: var(--accent); }
.card.pc.down { background: repeating-linear-gradient(135deg, var(--surface) 0 6px, var(--bg) 6px 12px); border-style: dashed; }
.card.pc.back { color: transparent; background: repeating-linear-gradient(135deg, var(--border) 0 6px, var(--bg) 6px 12px); border-color: var(--muted); }
.card.long { font-size: .8rem; }
.word .wtext { overflow-wrap: anywhere; }

/* ---- watching it move ---- */

.stage { position: relative; }
.stagebar { display: flex; justify-content: flex-end; }
.stage .card {
  position: absolute;
  left: 0;
  top: 0;
  min-width: 0;
  padding: 0;
  transition: background .2s ease, box-shadow .2s ease, color .2s ease;
}
.stage .card.top { box-shadow: 0 0 0 2px var(--accent); }
.stage .card.moved { box-shadow: 0 0 0 3px var(--accent); z-index: 5; }
.stage .card.matched { box-shadow: 0 0 0 2px var(--ok); }
.stage .card.wrong { box-shadow: 0 0 0 2px var(--danger); }
.stagepick {
  position: absolute;
  left: 0;
  width: 88px;
  padding: .15rem .2rem;
  font-size: .72rem;
  white-space: nowrap;
}
.stagelabel {
  position: absolute;
  left: 0;
  width: 88px;
  font-size: .75rem;
  line-height: 1.2;
  color: var(--text);
}
.stagelabel small { display: block; color: var(--muted); font-size: .68rem; }
.scrub { width: 100%; margin: .3rem 0 0; accent-color: var(--accent); }
#frameMsg { margin: .6rem 0 0; }