/* Playground Swing -- one stylesheet, no framework, no web fonts. */
:root {
  --bg: #f5f2ec; --panel: #ffffff; --ink: #1d242e; --dim: #5c6773;
  --line: #d9d2c6; --accent: #1668a8; --accent-ink: #ffffff;
  --warn: #b86b12; --good: #2c7a43; --bad: #b3352f;
  --chip: #eae5db; --chip-on: #1668a8; --kbd: #ece7de;
  --radius: 10px; --shadow: 0 1px 2px rgba(0,0,0,.06), 0 6px 18px rgba(0,0,0,.05);
}
html[data-theme="dark"] {
  --bg: #0e1218; --panel: #161b24; --ink: #e7edf5; --dim: #8a94a3;
  --line: #2a3340; --accent: #5ec8f2; --accent-ink: #0e1218;
  --warn: #f0a04b; --good: #7fd18e; --bad: #ef6f6c;
  --chip: #1e2532; --chip-on: #5ec8f2; --kbd: #222a36;
  --shadow: 0 1px 2px rgba(0,0,0,.4), 0 6px 18px rgba(0,0,0,.35);
}
* { box-sizing: border-box; }
html, body { margin: 0; padding: 0; }
body {
  background: var(--bg); color: var(--ink);
  font: 15px/1.55 ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-text-size-adjust: 100%;
}
main { max-width: 980px; margin: 0 auto; padding: 0 18px 60px; }

.top { max-width: 980px; margin: 0 auto; padding: 22px 18px 10px; }
.brand h1 { font-size: 30px; line-height: 1.15; margin: 0 0 4px; letter-spacing: -.01em; }
.tag { margin: 0 0 14px; color: var(--dim); max-width: 62ch; }
.topbar { display: flex; gap: 10px; align-items: center; flex-wrap: wrap;
  border-bottom: 1px solid var(--line); padding-bottom: 10px; }
.tabs { display: flex; gap: 6px; flex: 1 1 auto; }
button { font: inherit; cursor: pointer; }
.tab {
  background: transparent; border: 1px solid transparent; color: var(--dim);
  padding: 6px 12px; border-radius: 999px;
}
.tab.is-on { background: var(--chip); color: var(--ink); border-color: var(--line); }
.ghost { background: transparent; border: 1px solid var(--line); color: var(--ink);
  padding: 6px 12px; border-radius: 8px; }
.primary { background: var(--accent); color: var(--accent-ink); border: 1px solid var(--accent);
  padding: 7px 16px; border-radius: 8px; font-weight: 600; }
.chip { background: var(--chip); border: 1px solid var(--line); color: var(--ink);
  padding: 5px 11px; border-radius: 999px; }
.chip.is-on { background: var(--chip-on); color: var(--accent-ink); border-color: var(--chip-on); }

.view[hidden] { display: none !important; }

.stage { margin: 16px 0 10px; border: 1px solid var(--line); border-radius: var(--radius);
  overflow: hidden; box-shadow: var(--shadow); background: var(--panel); }
#scene { display: block; width: 100%; height: 46vh; min-height: 300px; max-height: 480px; }

.hud { display: grid; grid-template-columns: repeat(auto-fit, minmax(140px, 1fr)); gap: 8px; margin: 10px 0; }
.hud .cell { background: var(--panel); border: 1px solid var(--line); border-radius: 8px;
  padding: 8px 10px; display: flex; flex-direction: column; gap: 1px; }
.hud .cell.wide { grid-column: 1 / -1; }
.hud .k { font-size: 11px; text-transform: uppercase; letter-spacing: .06em; color: var(--dim); }
.hud .v { font: 600 19px/1.2 ui-monospace, SFMono-Regular, Menlo, monospace; }
.hud .cell.wide .v { font-size: 14px; font-weight: 500; }
.hud .u { font-size: 11px; color: var(--dim); }

.controls { display: flex; gap: 16px; flex-wrap: wrap; align-items: center; margin: 12px 0; }
.controls .group { display: flex; gap: 6px; align-items: center; flex-wrap: wrap; }
.controls .label { font-size: 11px; text-transform: uppercase; letter-spacing: .06em; color: var(--dim); }
.pad { display: flex; gap: 6px; align-items: center; flex-wrap: wrap; margin: 4px 0 10px; }
.pad .label { font-size: 11px; text-transform: uppercase; letter-spacing: .06em; color: var(--dim); }
.chip.hold { touch-action: none; user-select: none; -webkit-user-select: none;
  -webkit-touch-callout: none; padding: 9px 14px; }
.chip.hold.is-held { background: var(--chip-on); color: var(--accent-ink); border-color: var(--chip-on); }
.safety { color: var(--dim); font-size: 13px; max-width: 78ch; margin: 14px 0 0;
  border-left: 3px solid var(--line); padding-left: 10px; }
.hint { color: var(--dim); font-size: 13px; max-width: 78ch; }
kbd { background: var(--kbd); border: 1px solid var(--line); border-bottom-width: 2px;
  border-radius: 5px; padding: 1px 5px; font: 12px ui-monospace, SFMono-Regular, Menlo, monospace; }

.bars { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin: 10px 0 14px; }
.bar .k { font-size: 11px; text-transform: uppercase; letter-spacing: .06em; color: var(--dim); }
.bar .track { height: 8px; background: var(--chip); border-radius: 999px; overflow: hidden;
  border: 1px solid var(--line); }
.bar .fill { height: 100%; background: var(--accent); width: 0; }

.records { display: flex; gap: 18px; flex-wrap: wrap; color: var(--dim); font-size: 13px;
  border-top: 1px solid var(--line); padding-top: 10px; }
.records strong { color: var(--ink); font: 600 14px ui-monospace, SFMono-Regular, Menlo, monospace; }
.note { color: var(--warn); }

.tip { background: var(--panel); border: 1px solid var(--line); border-left: 3px solid var(--accent);
  border-radius: var(--radius); padding: 12px 16px; margin: 18px 0 0; }
.tip h2 { font-size: 15px; margin: 0 0 6px; }
.tip p { margin: 0; color: var(--dim); }
.tip em { color: var(--ink); font-style: normal; font-weight: 600; }

.prose { max-width: 72ch; }
.prose h2 { font-size: 22px; margin: 22px 0 8px; }
.prose h3 { font-size: 16px; margin: 20px 0 6px; }
.prose ul { padding-left: 20px; }
.prose li { margin: 6px 0; }
.card { background: var(--panel); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 16px 18px; margin: 18px 0; box-shadow: var(--shadow); }
.card h3 { font-size: 17px; margin: 0 0 8px; }
.card p { max-width: 74ch; }
/* Maths is set in a serif face, not a monospace one: in the system mono font
   the theta glyph is near-indistinguishable from a zero, which turned
   "l theta''" into "l0''" on the first render. */
.eq { font: 17px/1.5 ui-serif, Georgia, "Times New Roman", serif; background: var(--chip);
  border-radius: 6px; padding: 10px 14px; overflow-x: auto; letter-spacing: .01em; font-variant-numeric: lining-nums; }
.m { font: 15px ui-serif, Georgia, "Times New Roman", serif; letter-spacing: .01em; }
.fine { color: var(--dim); font-size: 13px; }
[data-fig] { font: 600 13px ui-monospace, SFMono-Regular, Menlo, monospace; color: var(--accent); }
.chart { border: 1px solid var(--line); border-radius: 8px; overflow: hidden; margin: 10px 0; }
.chart canvas { display: block; width: 100%; height: 300px; }

.tbl { width: 100%; border-collapse: collapse; font-size: 13px; display: block; overflow-x: auto; }
.tbl th, .tbl td { text-align: left; padding: 6px 10px; border-bottom: 1px solid var(--line); }
.tbl th { color: var(--dim); font-weight: 600; font-size: 11px; text-transform: uppercase;
  letter-spacing: .06em; }

code { font: 12px ui-monospace, SFMono-Regular, Menlo, monospace; background: var(--chip);
  padding: 1px 5px; border-radius: 4px; }
a { color: var(--accent); }
footer { max-width: 980px; margin: 0 auto; padding: 18px; border-top: 1px solid var(--line);
  color: var(--dim); font-size: 13px; }

@media (max-width: 640px) {
  .brand h1 { font-size: 24px; }
  .bars { grid-template-columns: 1fr; }
  #scene { height: 38vh; min-height: 240px; }
}