:root {
  --fg: #111; --bg: #fff; --muted: #555; --line: #111; --accent: #e0301e;
  --serif: ui-serif, "Iowan Old Style", "Charter", Georgia, Cambria, "Times New Roman", serif;
  --mono: ui-monospace, SFMono-Regular, Menlo, Consolas, "Liberation Mono", "DejaVu Sans Mono", monospace;
  --wrap: 76rem;
}
*, *::before, *::after { box-sizing: border-box; }
body { margin: 0; background: var(--bg); color: var(--fg); font-family: var(--serif); font-size: 1.0625rem; line-height: 1.55; }
.mono { font-family: var(--mono); }
.wrap { max-width: var(--wrap); margin: 0 auto; padding: 0 1.25rem; }
a { color: var(--fg); text-underline-offset: .18em; }
a:hover { text-decoration-color: var(--accent); }
:focus-visible { outline: 3px solid var(--accent); outline-offset: 3px; }
.visually-hidden { position: absolute !important; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }
.skip-link { position: absolute; left: 1rem; top: -4rem; background: var(--fg); color: var(--bg); padding: .5rem .9rem; font-family: var(--mono); z-index: 10; }
.skip-link:focus { top: 1rem; }

.site-header { border-bottom: 2px solid var(--line); }
.site-header .wrap { display: flex; align-items: center; gap: 1rem; padding-top: .9rem; padding-bottom: .9rem; }
.site-title { font-family: var(--mono); font-weight: 700; text-decoration: none; margin-right: auto; display: inline-flex; gap: .5rem; align-items: center; }
.site-title::before { content: ""; width: .7rem; height: .7rem; background: var(--accent); }
.site-title .sub { font-weight: 400; color: var(--muted); }
.ext, .lang-btn { font-family: var(--mono); font-size: .875rem; }
.lang { display: flex; gap: .25rem; }
.lang-btn { background: none; border: 0; padding: .25rem .35rem; cursor: pointer; color: var(--fg); text-decoration: underline; }
.lang-btn[aria-pressed="true"] { font-weight: 700; text-decoration: none; box-shadow: inset 0 -3px 0 var(--accent); }

main { padding: 2rem 0 3rem; }
h1 { font-size: clamp(1.9rem, 4.5vw, 3rem); line-height: 1.15; margin: 0 0 .75rem; font-weight: 600; }
h2 { font-size: 1.25rem; margin: 0 0 .6rem; font-weight: 600; }
h3 { font-size: 1rem; margin: 1rem 0 .3rem; font-family: var(--mono); text-transform: uppercase; letter-spacing: .06em; }
.intro { max-width: 46rem; margin: 0 0 1.5rem; }

.machine-panel { border-top: 2px solid var(--line); border-bottom: 2px solid var(--line); padding: 1rem 0 1.25rem; }
.status { display: flex; flex-wrap: wrap; gap: .4rem 1.25rem; font-size: .85rem; align-items: center; }
.status .mode { border: 1px solid var(--fg); padding: .1rem .5rem; }
.notice.is-stop { background: #fff3f1; padding: .5rem .75rem; }
.busy { color: var(--muted); }

/* tape */
.tape { --n: 21; --head: 7; position: relative; margin: 1.25rem 0 .5rem; padding-top: 92px; }
.rail { position: absolute; left: 0; right: 0; top: 30px; height: 6px; background: var(--fg); }
.motor { position: absolute; left: -2px; top: -16px; width: 36px; height: 36px; background: var(--fg); border-radius: 2px; }
.motor::after { content: ""; position: absolute; inset: 11px; background: var(--bg); border-radius: 50%; }
.cells { display: grid; grid-template-columns: repeat(var(--n), minmax(0, 1fr)); gap: 4px; border-bottom: 4px solid var(--fg); padding-bottom: 8px; }
.cell { aspect-ratio: 1 / 2.2; border: 2px solid var(--fg); background: var(--bg); }
.cell.on { background: var(--fg); }
.cell.under { outline: 3px solid var(--accent); outline-offset: 2px; }
.cell.flip { animation: flip .22s ease-in-out; }
@keyframes flip { 0% { transform: scaleX(1); } 50% { transform: scaleX(0.04); } 100% { transform: scaleX(1); } }
.head { position: absolute; top: 14px; width: calc((100% - (var(--n) - 1) * 4px) / var(--n)); left: 0;
  transform: translateX(calc(var(--head) * (100% + 4px))); transition: transform .35s ease-in-out; display: flex; flex-direction: column; align-items: center; }
.carriage { width: 150%; min-width: 26px; height: 36px; background: var(--fg); }
.pointer { width: 0; height: 0; border-left: 9px solid transparent; border-right: 9px solid transparent; border-top: 14px solid var(--accent); margin-top: 22px; }
.camera { position: absolute; bottom: -4px; height: calc(100% - 82px); pointer-events: none;
  width: calc(9 * (100% - (var(--n) - 1) * 4px) / var(--n) + 8 * 4px + 8px);
  left: calc((var(--head) - 4) * ((100% - (var(--n) - 1) * 4px) / var(--n) + 4px) - 4px);
  border: 1.5px dashed var(--muted); transition: left .35s ease-in-out; }
.camera span { position: absolute; top: -1.4rem; left: 0; font-family: var(--mono); font-size: .72rem; color: var(--muted); }

.say-wrap { min-height: 3.2em; margin: 1.5rem 0 1rem; font-size: clamp(1.1rem, 2.4vw, 1.45rem); line-height: 1.35; max-width: 52rem; }
.say:not(:empty)::before { content: "AI › "; font-family: var(--mono); font-size: .8em; color: var(--accent); }

.controls { display: flex; flex-wrap: wrap; gap: .9rem 1.5rem; align-items: flex-end; font-family: var(--mono); font-size: .85rem; }
.field { display: flex; flex-direction: column; gap: .25rem; }
select, button { font: inherit; color: var(--fg); background: var(--bg); border: 2px solid var(--fg); padding: .4rem .7rem; border-radius: 0; }
button { cursor: pointer; }
button:hover:not(:disabled) { box-shadow: inset 0 -3px 0 var(--accent); }
button.primary, button[aria-pressed="true"]#play { background: var(--fg); color: var(--bg); }
button:disabled { opacity: .45; cursor: not-allowed; }
.buttons { display: flex; flex-wrap: wrap; gap: .5rem; }
.range-row { display: flex; align-items: center; gap: .5rem; }
input[type=range] { accent-color: var(--accent); width: 9rem; }
.toggles { display: flex; gap: 1rem; }
.toggles input { accent-color: var(--accent); width: 1.05rem; height: 1.05rem; vertical-align: -2px; }
.notice { margin: 1rem 0 0; font-family: var(--mono); font-size: .82rem; border-left: 4px solid var(--accent); padding-left: .75rem; max-width: 52rem; color: var(--fg); }

.panels { display: grid; grid-template-columns: 1fr 1fr; gap: 2rem; margin-top: 2rem; }
@media (max-width: 52rem) { .panels { grid-template-columns: 1fr; } }
.story, .log { height: 26rem; overflow-y: auto; border-top: 2px solid var(--line); padding-top: .75rem; }
.story p { margin: 0 0 .7rem; }
.story .tag { font-family: var(--mono); font-size: .75rem; color: var(--muted); }
.story p.err .tag::after { content: " ■"; color: var(--accent); }
.story p.justify { margin-left: 1.25rem; padding-left: .75rem; border-left: 3px solid var(--accent); font-style: italic; }
.story p.justify .tag { font-style: normal; }
.story .epilogue { font-size: 1.1rem; }
.empty { color: var(--muted); font-style: italic; }
.log { list-style: none; margin: 0; padding-left: 0; font-size: .78rem; line-height: 1.6; }
.log li { overflow-wrap: anywhere; padding: .1rem 0; border-bottom: 1px solid #e6e6e6; }
.log li.err { box-shadow: inset 4px 0 0 var(--accent); padding-left: .6rem; }

.about { margin-top: 2.5rem; border-top: 2px solid var(--line); padding-top: 1rem; max-width: 46rem; }
.table-scroll { overflow-x: auto; }
table.data { border-collapse: collapse; font-size: .82rem; width: 100%; min-width: 20rem; }
table.data caption { text-align: left; color: var(--muted); padding-bottom: .4rem; }
table.data th, table.data td { text-align: left; padding: .4rem .75rem .4rem 0; border-bottom: 1px solid var(--line); }
table.data thead th { border-bottom: 2px solid var(--line); }

.site-footer { border-top: 2px solid var(--line); font-family: var(--mono); font-size: .78rem; }
.site-footer .wrap { padding-top: 1rem; padding-bottom: 1.5rem; }
.site-footer p { margin: 0; }

@media (max-width: 40rem) {
  .tape { padding-top: 76px; }
  .carriage { height: 28px; }
  .pointer { margin-top: 16px; }
  .rail { top: 24px; }
  .story, .log { height: 20rem; }
}
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; }
}
[hidden] { display: none !important; }
.cell { min-width: 0; }
@media (max-width: 40rem) {
  .site-title .sub { display: none; }
  .site-header .wrap { gap: .6rem; }
}