/* coach — marked-paper theme.
   Cool paper, blue-black ink, one ballpoint accent. Red and green are
   reserved for grading marks; yellow is the highlighter. */

:root {
  --paper: #f5f6f2;
  --card: #fdfdfb;
  --ink: #212b33;
  --dim: #68716b;
  --line: #d8dcd2;
  --pen: #2957cb;
  --pen-deep: #1e409a;
  --right: #2e7d4e;
  --wrong: #c0392b;
  --highlight: #f7dd6b;

  --serif: "Zilla Slab", "Rockwell", serif;
  --sans: "IBM Plex Sans", system-ui, sans-serif;
  --mono: "IBM Plex Mono", ui-monospace, monospace;
}

* { box-sizing: border-box; margin: 0; }

/* class display rules must never resurrect [hidden] elements */
[hidden] { display: none !important; }

html { height: 100%; }

body {
  min-height: 100%;
  background: var(--paper);
  color: var(--ink);
  font: 400 1rem/1.6 var(--sans);
  display: flex;
  flex-direction: column;
  -webkit-font-smoothing: antialiased;
}

.mono { font-family: var(--mono); }

.visually-hidden {
  position: absolute; width: 1px; height: 1px;
  clip-path: inset(50%); overflow: hidden; white-space: nowrap;
}

:focus-visible { outline: 2px solid var(--pen); outline-offset: 3px; border-radius: 2px; }

/* ── Frame ─────────────────────────────────────────────── */

.site-head, main, .site-foot {
  width: 100%;
  max-width: 42rem;
  margin-inline: auto;
  padding-inline: 1.25rem;
}

.site-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  padding-top: 1.5rem;
}

.wordmark {
  font-family: var(--mono);
  font-size: .85rem;
  letter-spacing: .08em;
  color: var(--dim);
  background: none;
  border: none;
  padding: 0;
  cursor: pointer;
}
.wordmark:hover { color: var(--pen-deep); }
.wordmark::before { content: "◉ "; color: var(--pen); }

.head-right {
  display: flex;
  align-items: center;
  gap: 1rem;
}

.user-chip {
  display: inline-flex;
  align-items: center;
  gap: .1rem;
  font-size: .8rem;
  color: var(--dim);
}
.user-chip .btn { font-size: .8rem; padding: .2rem .5rem; }

.set-switch select {
  font: 500 .8rem var(--mono);
  color: var(--ink);
  background: transparent;
  border: 1px solid var(--line);
  border-radius: 3px;
  padding: .25rem .4rem;
  max-width: 14rem;
}

main { flex: 1; padding-block: 2.25rem 3rem; }

.site-foot {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  padding-block: .75rem 1.25rem;
  color: var(--dim);
  font-size: .75rem;
  min-height: 2.5rem;
}

.foot-repo {
  margin-left: auto;   /* stays right even when the keys hint is hidden */
  color: var(--dim);
  text-decoration: none;
  border-bottom: 1px dotted var(--line);
  white-space: nowrap;
}
.foot-repo:hover, .foot-repo:focus-visible { color: var(--pen); border-bottom-color: var(--pen); }

/* ── Type ──────────────────────────────────────────────── */

.subject {
  font: 600 2.1rem/1.2 var(--serif);
  letter-spacing: -.01em;
  text-transform: lowercase;
}
.subject.small { font-size: 1.4rem; }

.subject-meta { color: var(--dim); margin-top: .35rem; }

.hint { color: var(--dim); font-size: .85rem; margin-top: 1.25rem; }

/* ── Menu: table of contents ───────────────────────────── */

.contents { margin-top: 2.25rem; }

.contents-head {
  font: 500 .75rem var(--mono);
  text-transform: lowercase;
  letter-spacing: .14em;
  color: var(--dim);
  margin: 1.75rem 0 .5rem;
  border-bottom: 1px solid var(--line);
  padding-bottom: .35rem;
}

.toc { list-style: none; padding: 0; }

.toc-row {
  display: flex;
  align-items: baseline;
  gap: .75rem;
  width: 100%;
  padding: .55rem .25rem;
  background: none;
  border: none;
  font: inherit;
  color: inherit;
  text-align: left;
  cursor: pointer;
  border-radius: 3px;
}
.toc-row:hover .toc-label { color: var(--pen-deep); }
.toc-row:hover .toc-key { background: var(--pen); color: var(--card); border-color: var(--pen); }

.toc-key {
  font: 500 .8rem/1.5 var(--mono);
  border: 1px solid var(--line);
  border-radius: 3px;
  min-width: 1.5rem;
  text-align: center;
  color: var(--dim);
  transition: background .12s, color .12s;
}

.toc-label { font-weight: 500; text-transform: lowercase; }
.toc-sub { color: var(--dim); font-weight: 400; text-transform: lowercase; }

.toc-leader {
  flex: 1;
  min-width: 2rem;
  border-bottom: 2px dotted var(--line);
  transform: translateY(-.3em);
}

.toc-count { font: 400 .85rem var(--mono); color: var(--dim); }

.session-banner {
  margin-top: 1.25rem;
  font-family: var(--mono);
  font-size: .9rem;
  border-left: 3px solid var(--pen);
  padding: .5rem .8rem;
  background: var(--card);
}

/* ── Quiz ──────────────────────────────────────────────── */

.quiz-head {
  display: flex;
  align-items: center;
  gap: 1rem;
  font-size: .85rem;
  color: var(--dim);
}

.counter { font-weight: 500; color: var(--ink); white-space: nowrap; }

.track {
  flex: 1;
  height: 3px;
  background: var(--line);
  border-radius: 2px;
  overflow: hidden;
}
.track-fill {
  height: 100%;
  width: 0;
  background: var(--pen);
  transition: width .3s ease;
}

.q-meta { white-space: nowrap; font-size: .78rem; text-transform: lowercase; }

.focus-note { margin-top: 1rem; color: var(--pen-deep); font-size: .9rem; text-transform: lowercase; }

.question {
  font: 500 1.45rem/1.45 var(--serif);
  margin-top: 1.75rem;
}

.multi-note {
  margin-top: .5rem;
  color: var(--dim);
  font-size: .85rem;
  font-style: italic;
}

/* Scantron rows — the answer sheet */

.options {
  list-style: none;
  padding: 0;
  margin-top: 1.5rem;
  display: grid;
  gap: .5rem;
}

.option {
  display: flex;
  align-items: center;
  gap: .9rem;
  width: 100%;
  padding: .7rem .85rem;
  font: inherit;
  text-align: left;
  color: inherit;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 4px;
  cursor: pointer;
  transition: border-color .12s;
}
.option:hover:not(:disabled) { border-color: var(--pen); }
.option:disabled { cursor: default; }

.bubble {
  flex: none;
  width: 1.9rem;
  height: 1.9rem;
  border: 2px solid var(--ink);
  border-radius: 50%;
  display: grid;
  place-items: center;
  font: 500 .85rem var(--mono);
  text-transform: lowercase;
  transition: background .12s, color .12s, border-color .12s;
}

.option[aria-pressed="true"] { border-color: var(--pen); }
.option[aria-pressed="true"] .bubble {
  background: var(--pen);
  border-color: var(--pen);
  color: var(--card);
}

/* Grading marks */
.option.is-right { border-color: var(--right); }
.option.is-right .bubble { background: var(--right); border-color: var(--right); color: var(--card); }
.option.is-wrong { border-color: var(--wrong); }
.option.is-wrong .bubble { background: var(--wrong); border-color: var(--wrong); color: var(--card); }
.option.is-wrong .option-text { text-decoration: line-through; text-decoration-color: var(--wrong); }
.option.is-faded { opacity: .55; }

.mark { margin-left: auto; font-weight: 600; font-family: var(--mono); }
.mark.right { color: var(--right); }
.mark.wrong { color: var(--wrong); }

.verdict {
  margin-top: 1.5rem;
  font: 600 1.1rem var(--serif);
  text-transform: lowercase;
}
.verdict.right { color: var(--right); }
.verdict.wrong { color: var(--wrong); }

.explanation {
  margin-top: .9rem;
  padding: .75rem 1rem;
  background: var(--card);
  border-left: 4px solid var(--highlight);
  color: var(--ink);
}
.explanation::before {
  content: "explanation";
  display: block;
  font: 500 .7rem var(--mono);
  letter-spacing: .14em;
  color: var(--dim);
  margin-bottom: .3rem;
}

.quiz-actions {
  margin-top: 1.75rem;
  display: flex;
  align-items: center;
  gap: .75rem;
  flex-wrap: wrap;
}

.warn { color: var(--wrong); font-size: .85rem; margin-top: .75rem; }

/* ── Buttons ───────────────────────────────────────────── */

.btn {
  font: 500 .95rem var(--sans);
  padding: .5rem 1.1rem;
  border-radius: 4px;
  border: 1px solid var(--ink);
  background: var(--card);
  color: var(--ink);
  cursor: pointer;
  text-transform: lowercase;
}
.btn:hover { border-color: var(--pen); color: var(--pen-deep); }

.btn.primary {
  background: var(--pen);
  border-color: var(--pen);
  color: var(--card);
}
.btn.primary:hover { background: var(--pen-deep); border-color: var(--pen-deep); color: var(--card); }
.btn.primary:disabled { opacity: .45; cursor: default; background: var(--pen); border-color: var(--pen); color: var(--card); }

.btn.quiet {
  border-color: transparent;
  background: transparent;
  color: var(--dim);
}
.btn.quiet:hover { color: var(--pen-deep); }

kbd {
  font: 500 .75rem var(--mono);
  border: 1px solid var(--line);
  border-bottom-width: 2px;
  border-radius: 3px;
  padding: 0 .35em;
  background: var(--card);
}

/* ── Session summary ───────────────────────────────────── */

.session-line {
  margin-top: 1rem;
  font: 500 1.2rem var(--serif);
}

/* ── Dashboard ─────────────────────────────────────────── */

.dash {
  width: 100%;
  margin-top: 1.75rem;
  border-collapse: collapse;
  font-size: .92rem;
}
.dash th {
  font: 500 .7rem var(--mono);
  text-transform: lowercase;
  letter-spacing: .12em;
  color: var(--dim);
  text-align: left;
  border-bottom: 1px solid var(--line);
  padding: .4rem .5rem .4rem 0;
}
.dash td { padding: .5rem .5rem .5rem 0; border-bottom: 1px solid var(--line); vertical-align: middle; }
.dash td:first-child { text-transform: lowercase; }
.dash td.num { font-family: var(--mono); font-size: .85rem; white-space: nowrap; }

.acc-bar {
  width: 100%;
  min-width: 4.5rem;
  height: .55rem;
  background: var(--line);
  border-radius: 2px;
  overflow: hidden;
}
.acc-fill { height: 100%; }
.acc-fill.good { background: var(--right); }
.acc-fill.mid { background: var(--highlight); }
.acc-fill.bad { background: var(--wrong); }

.dash-line { margin-top: 1rem; }
.dash-line strong { font-weight: 600; }

.focus-mark {
  background: linear-gradient(transparent 45%, var(--highlight) 45%, var(--highlight) 92%, transparent 92%);
  padding-inline: .15em;
  text-transform: lowercase;
}

/* ── Tutor ─────────────────────────────────────────────── */

.tutor-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
}

.chat {
  margin-top: 1.25rem;
  display: grid;
  gap: 1rem;
  min-height: 8rem;
}

.msg { display: flex; gap: .75rem; }
.msg-who {
  flex: none;
  font: 500 .8rem/1.8 var(--mono);
  color: var(--dim);
  min-width: 3.6rem;
  text-align: right;
}
.msg.you .msg-who { color: var(--pen-deep); }
.msg.tutor .msg-who { color: var(--right); }
.msg-body { white-space: pre-wrap; overflow-wrap: anywhere; }
.msg.you .msg-body { font-weight: 500; }

.chat-form {
  margin-top: 1.5rem;
  display: flex;
  align-items: center;
  gap: .6rem;
  border-top: 1px solid var(--line);
  padding-top: 1rem;
}
.chat-prompt { color: var(--pen-deep); font-size: .85rem; }
.chat-form input {
  flex: 1;
  font: inherit;
  color: inherit;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: .5rem .75rem;
}
.chat-form input:focus-visible { outline-offset: 0; }

/* ── Sign in ───────────────────────────────────────────── */

.auth-form {
  margin-top: 2rem;
  display: grid;
  gap: 1.1rem;
  max-width: 22rem;
}

.field { display: grid; gap: .35rem; }

.field-label {
  font: 500 .75rem var(--mono);
  letter-spacing: .12em;
  color: var(--dim);
}

.field input {
  font: inherit;
  color: inherit;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 4px;
  padding: .55rem .75rem;
}
.field input:focus-visible { outline-offset: 0; }

.auth-actions {
  display: flex;
  align-items: center;
  gap: .75rem;
  flex-wrap: wrap;
}

/* ── Notices ───────────────────────────────────────────── */

.notice {
  margin-top: 1.5rem;
  padding: .6rem .9rem;
  border-left: 3px solid var(--highlight);
  background: var(--card);
}

/* ── Small screens ─────────────────────────────────────── */

@media (max-width: 480px) {
  .subject { font-size: 1.7rem; }
  .question { font-size: 1.25rem; }
  .q-meta { display: none; }
  .msg-who { min-width: 2.8rem; }
  .toc-sub { display: none; }
  .toc-label { white-space: nowrap; }
}

/* keyboard hints are noise without a keyboard */
@media (hover: none) and (pointer: coarse) {
  #foot-keys { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; }
}