*, *::before, *::after { box-sizing: border-box; }
[hidden] { display: none !important; }
img { max-width: 100%; }
html { -webkit-text-size-adjust: 100%; }
/* Layout: one working column. The two options get equal width and identical treatment; nothing on the page favours a side. */
:root {
  --bg: #dfdedb; --surface: #d3d2ce; --panel: #f1f0ed; --ink: #26251e; --muted: #5a5850; --line: #bdbcb7;
  --action: #2456d6; --action-ink: #ffffff; --warn: #8a4b08; --good: #1c6b3a;
  --font-text: "Familjen Grotesk", system-ui, sans-serif;
  --font-mono: "IBM Plex Mono", "Noto Sans Math", ui-monospace, Menlo, Consolas, monospace;
  --m-in: 140ms; --m-out: 200ms; --m-press: 90ms; --m-ease: cubic-bezier(.2,.8,.2,1);
  --r: 3px;
}
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) {
  --bg: #1d1d19; --surface: #29281f; --panel: #26251e; --ink: #e6e5df; --muted: #a5a39b; --line: #45443c;
  --action: #8fafff; --action-ink: #10131c; --warn: #e0a868; --good: #7fcf9b; color-scheme: dark } }
:root[data-theme="dark"] {
  --bg: #1d1d19; --surface: #29281f; --panel: #26251e; --ink: #e6e5df; --muted: #a5a39b; --line: #45443c;
  --action: #8fafff; --action-ink: #10131c; --warn: #e0a868; --good: #7fcf9b; color-scheme: dark }

body { margin: 0; background: var(--bg); color: var(--ink); font: 400 16px/1.55 var(--font-text); }
.wrap { max-width: 1320px; margin-inline: auto; padding-inline: clamp(16px, 3vw, 40px); }
.narrow { max-width: 680px; margin-inline: auto; padding-inline: 16px; padding-block: clamp(32px, 8vh, 88px); display: grid; gap: 24px; }
h1 { font-weight: 400; font-size: clamp(2.1rem, 5vw, 3.1rem); letter-spacing: -0.03em; line-height: 1.08; margin: 0; text-wrap: balance; }
h2 { font-weight: 500; font-size: 1.05rem; margin: 0; }
p { margin: 0; }
.muted { color: var(--muted); }
ul.plain { margin: 0; padding-left: 1.15em; display: grid; gap: 8px; }

.field { display: grid; gap: 6px; }
.field label, .field .label { font-weight: 500; font-size: .95rem; }
input[type=text], select, textarea {
  font: inherit; color: var(--ink); background: var(--panel); border: 1px solid var(--line); border-radius: var(--r);
  padding: 10px 12px; width: 100%; transition: border-color var(--m-in) var(--m-ease), box-shadow var(--m-in) var(--m-ease);
}
input[type=text]:focus, select:focus, textarea:focus { outline: none; border-color: var(--action); box-shadow: 0 0 0 3px color-mix(in srgb, var(--action) 25%, transparent); }
.check { display: flex; gap: 10px; align-items: flex-start; }
.check input { margin-top: .35em; width: 18px; height: 18px; flex: none; accent-color: var(--action); }

.btn {
  font: 500 1rem/1.2 var(--font-text); min-height: 48px; padding: 12px 22px; border-radius: var(--r); cursor: pointer;
  border: 1px solid var(--action); background: var(--action); color: var(--action-ink);
  transition: transform var(--m-in) var(--m-ease), background-color var(--m-in) var(--m-ease), border-color var(--m-in) var(--m-ease);
}
.btn.quiet { background: transparent; color: var(--ink); border-color: var(--line); }
.btn:disabled { opacity: .45; cursor: not-allowed; }
@media (hover: hover) and (pointer: fine) {
  .btn:not(:disabled):hover { transform: translateY(-1px); background: color-mix(in srgb, var(--action) 86%, var(--ink)); }
  .btn.quiet:not(:disabled):hover { background: color-mix(in srgb, var(--ink) 7%, transparent); border-color: var(--muted); }
  .choice:not(:disabled):hover { transform: translateY(-1px); background: color-mix(in srgb, var(--ink) 9%, var(--panel)); border-color: var(--ink); }
  .textbtn:hover { color: var(--ink); text-decoration-color: currentColor; }
}
.btn:not(:disabled):active, .choice:not(:disabled):active { transform: translateY(1px) scale(.985); transition-duration: var(--m-press); }
:focus-visible { outline: 2px solid var(--action); outline-offset: 2px; }
.textbtn { background: none; border: 0; padding: 0; font: inherit; font-size: .9rem; color: var(--muted); cursor: pointer; text-decoration: underline; text-decoration-color: var(--line); text-underline-offset: 3px; }

.screen { min-height: 100dvh; display: flex; flex-direction: column; }
.screen > .wrap { flex: 1; width: 100%; }
.chooser .wrap { width: 100%; }
.topbar { position: sticky; top: env(safe-area-inset-top, 0px); z-index: 3; background: var(--bg); border-bottom: 1px solid var(--line); }
.topbar .wrap { display: flex; align-items: center; gap: 16px; padding-block: 10px; }
.count { font-variant-numeric: tabular-nums; font-size: .95rem; white-space: nowrap; }
.track { flex: 1; height: 3px; background: var(--line); min-width: 40px; }
.track span { display: block; height: 100%; background: var(--ink); }
.level { font-size: .95rem; font-weight: 500; white-space: nowrap; }
.saved { font-size: .85rem; color: var(--muted); white-space: nowrap; }
.saved.bad { color: var(--warn); }
.error { color: var(--warn); font-size: .95rem; }

.brief { display: grid; grid-template-columns: minmax(0, 3fr) minmax(0, 2fr); gap: 16px 40px; padding-block: 20px; }
.brief .block { display: grid; gap: 6px; align-content: start; min-width: 0; }
.eyebrow { font-size: .82rem; font-weight: 500; color: var(--muted); }
.brief ol { margin: 0; padding-left: 1.3em; display: grid; gap: 6px; }
.figure { margin-top: 8px; background: #fff; border-radius: var(--r); padding: 8px; max-width: min(100%, 340px); }
.figure img { display: block; width: 100%; height: auto; }
.question { font-size: 1.15rem; font-weight: 500; padding-block: 8px 12px; border-top: 1px solid var(--line); text-wrap: balance; }

.options { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 16px; padding-bottom: 24px; align-items: stretch; }
.option { background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); min-width: 0; display: flex; flex-direction: column; }
.option h3 { margin: 0; font-size: .95rem; font-weight: 500; padding: 8px 16px; border-bottom: 1px solid var(--line); }
.option .body { padding: 14px 16px 18px; min-width: 0; overflow-x: auto; }
.code { margin: 0; font: 400 .875rem/1.6 var(--font-mono); white-space: pre-wrap; overflow-wrap: anywhere; tab-size: 2; }
.prose { font-size: 1rem; line-height: 1.65; display: grid; gap: 12px; }
.prose .katex-display { margin: .4em 0; overflow-x: auto; overflow-y: hidden; }

.chooser { position: sticky; bottom: 0; z-index: 3; background: var(--bg); border-top: 1px solid var(--line); padding-bottom: env(safe-area-inset-bottom, 0px); }
.chooser .wrap { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 16px; padding-block: 12px; }
.choice {
  font: 500 1rem/1.2 var(--font-text); min-height: 52px; padding: 12px; border-radius: var(--r); cursor: pointer; width: 100%;
  background: var(--panel); color: var(--ink); border: 1px solid var(--muted);
  transition: transform var(--m-in) var(--m-ease), background-color var(--m-in) var(--m-ease), border-color var(--m-in) var(--m-ease);
}
kbd { font: 400 .78rem var(--font-mono); border: 1px solid var(--line); border-radius: 2px; padding: 0 5px; color: var(--muted); margin-left: 6px; }
.footnote { display: flex; flex-wrap: wrap; gap: 8px 24px; padding-bottom: 28px; }
.report { display: grid; gap: 8px; padding-bottom: 28px; max-width: 640px; }
.actions { display: flex; flex-wrap: wrap; gap: 12px; }
.results { font: 400 .78rem/1.4 var(--font-mono); height: 120px; }
.notice { padding: 12px 14px; background: var(--surface); border-radius: var(--r); font-size: .95rem; }

/* Training */
.train { max-width: 860px; margin-inline: auto; padding-inline: 16px; padding-block: clamp(28px, 6vh, 64px); display: grid; gap: 20px; }
.train > * { min-width: 0; }
.train-title { font-size: clamp(1.8rem, 4vw, 2.5rem); }
.stack { display: grid; gap: 16px; min-width: 0; }
.codebox { background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); padding: 14px 16px; min-width: 0; }
.anatomy .part {
  font: inherit; color: inherit; text-align: left; white-space: pre-wrap; overflow-wrap: anywhere; display: inline; cursor: pointer; padding: 1px 2px;
  background: color-mix(in srgb, var(--action) 13%, transparent); border: 0; border-bottom: 2px solid var(--action); border-radius: 2px;
  transition: background-color var(--m-in) var(--m-ease);
  -webkit-box-decoration-break: clone; box-decoration-break: clone;
}
.anatomy .part.seen { border-bottom-color: var(--muted); background: color-mix(in srgb, var(--ink) 8%, transparent); }
.anatomy .part.active { background: var(--action); color: var(--action-ink); border-bottom-color: var(--action); }
.explain { background: var(--surface); border-radius: var(--r); padding: 14px 16px; display: grid; gap: 8px; min-width: 0; }
.explain[hidden] { display: none; }
.item { display: grid; gap: 10px; padding-block: 8px; min-width: 0; }
.opts { display: grid; gap: 8px; }
.opt {
  font: inherit; text-align: left; color: var(--ink); background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); padding: 10px 14px; cursor: pointer; min-height: 44px;
  transition: transform var(--m-in) var(--m-ease), background-color var(--m-in) var(--m-ease), border-color var(--m-in) var(--m-ease);
}
.opt.selected { border-color: var(--action); box-shadow: inset 0 0 0 1px var(--action); }
.opt.right { border-color: var(--good); box-shadow: inset 0 0 0 1px var(--good); }
.opt.wrong { border-color: var(--warn); color: var(--muted); }
.feedback { font-size: .95rem; min-height: 1.5em; }
.cards { display: grid; grid-template-columns: minmax(0, 2fr) minmax(0, 3fr); gap: 16px; align-items: start; }
.names { display: grid; gap: 6px; }
.name {
  font: 400 .84rem/1.3 var(--font-mono); text-align: left; overflow-wrap: anywhere; color: var(--ink); background: var(--panel); border: 1px solid var(--line); border-radius: var(--r); padding: 10px 12px; cursor: pointer;
  transition: transform var(--m-in) var(--m-ease), background-color var(--m-in) var(--m-ease), border-color var(--m-in) var(--m-ease);
}
.name.seen { border-color: var(--muted); }
.name.active { background: var(--action); color: var(--action-ink); border-color: var(--action); }
@media (hover: hover) and (pointer: fine) {
  .opt:hover { transform: translateY(-1px); border-color: var(--muted); }
  .name:not(.active):hover { transform: translateY(-1px); border-color: var(--ink); }
  .anatomy .part:not(.active):hover { background: color-mix(in srgb, var(--action) 26%, transparent); }
}
.opt:active, .name:active { transform: translateY(1px) scale(.985); transition-duration: var(--m-press); }

@media (max-width: 860px) {
  .cards { grid-template-columns: minmax(0, 1fr); }
  .brief { grid-template-columns: minmax(0, 1fr); }
  .options { grid-template-columns: minmax(0, 1fr); }
  kbd { display: none; }
  .saved { display: none; }
}
@media (max-width: 480px) { .level { display: none; } }
@media (prefers-reduced-motion: reduce) { * { transition: none !important; } }