:root {
  --paper: #f7f4ec;
  --card: #fffdf8;
  --ink: #1f2a37;
  --muted: #5d6673;
  --line: #e4ddcc;
  --accent: #0f7a6b;
  --accent-ink: #ffffff;
  --accent-soft: #d9efe9;
  --good: #1d7a3a;
  --good-soft: #e1f3e5;
  --bad: #b3361f;
  --bad-soft: #fbe6e1;
  --warn-soft: #fff4d6;
  --shadow: 0 1px 0 rgba(31, 42, 55, .04), 0 6px 18px -10px rgba(31, 42, 55, .25);
  --radius: 14px;
}
@media (prefers-color-scheme: dark) {
  :root {
    --paper: #15191f;
    --card: #1d232b;
    --ink: #e9e6de;
    --muted: #9aa3ad;
    --line: #2e3640;
    --accent: #3cc4ae;
    --accent-ink: #0d1a17;
    --accent-soft: #1d3a35;
    --good: #5fd28a;
    --good-soft: #1b3324;
    --bad: #ff8a73;
    --bad-soft: #3a211c;
    --warn-soft: #3a3320;
    --shadow: 0 6px 18px -10px rgba(0, 0, 0, .6);
  }
}

* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: "Atkinson Hyperlegible", system-ui, sans-serif;
  font-size: 17px;
  line-height: 1.55;
}
h1, h2 { font-family: "Fraunces", Georgia, serif; line-height: 1.15; margin: 0 0 .5rem; }
h1 { font-size: clamp(1.8rem, 5vw, 2.6rem); }
h2 { font-size: 1.15rem; }
[hidden] { display: none !important; }

.topbar {
  position: sticky; top: 0; z-index: 5;
  display: flex; align-items: center; justify-content: space-between;
  padding: .6rem 1rem;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--line);
}
.brand {
  display: flex; align-items: center; gap: .5rem;
  background: none; border: 0; color: var(--ink); cursor: pointer;
  font: 700 1.1rem "Fraunces", Georgia, serif; padding: 0;
}
.brand svg { width: 28px; height: 28px; color: var(--accent); }
.stats { display: flex; gap: .9rem; color: var(--muted); font-size: .9rem; }
.stat b { color: var(--ink); font-size: 1.05rem; }

main { max-width: 760px; margin: 0 auto; padding: 1.25rem 1rem 4rem; }

.hero { padding: 1.5rem 0 1rem; }
.eyebrow { color: var(--accent); font-weight: 700; font-size: .85rem; letter-spacing: .04em; text-transform: uppercase; margin: 0 0 .5rem; }
.lede { color: var(--muted); max-width: 34rem; margin: 0 0 1.25rem; }

.topics { display: grid; gap: .75rem; grid-template-columns: repeat(auto-fill, minmax(220px, 1fr)); margin-top: 1rem; }
.topic {
  text-align: left; cursor: pointer;
  background: var(--card); color: var(--ink);
  border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1rem; box-shadow: var(--shadow);
  font: inherit; display: flex; flex-direction: column; gap: .35rem;
  transition: transform .12s ease, border-color .12s ease;
}
.topic:hover, .topic:focus-visible { transform: translateY(-2px); border-color: var(--accent); outline: none; }
.topic strong { font-size: 1.02rem; }
.topic .desc { color: var(--muted); font-size: .9rem; }
.meter { height: 6px; border-radius: 3px; background: var(--line); overflow: hidden; margin-top: .4rem; }
.meter i { display: block; height: 100%; background: var(--accent); border-radius: 3px; }
.topic .score { font-size: .8rem; color: var(--muted); }
.reset { text-align: center; margin-top: 2rem; }

.card {
  background: var(--card); border: 1px solid var(--line); border-radius: var(--radius);
  padding: 1.1rem 1.15rem; margin-bottom: 1rem; box-shadow: var(--shadow);
}
.q-head { display: flex; justify-content: space-between; align-items: center; margin-bottom: .75rem; }
.chip {
  background: var(--accent-soft); color: var(--accent); font-weight: 700;
  font-size: .82rem; padding: .25rem .65rem; border-radius: 999px;
}
.prompt { font-size: 1.05rem; }
.display { font-size: 1.2rem; overflow-x: auto; padding: .4rem 0 .1rem; }
.display .katex-display { margin: .6rem 0; }

.worklines { list-style: none; counter-reset: line; padding: 0; margin: .75rem 0 0; border-top: 1px dashed var(--line); }
.worklines li {
  counter-increment: line; display: grid; grid-template-columns: 4.2rem 1fr; align-items: center;
  border-bottom: 1px dashed var(--line); padding: .25rem 0; overflow-x: auto;
}
.worklines li::before { content: "Line " counter(line); color: var(--muted); font-size: .85rem; font-weight: 700; }
.worklines .katex-display { margin: .35rem 0; text-align: left; }
.worklines .katex-display > .katex { text-align: left; }

.label { display: block; font-weight: 700; font-size: .85rem; color: var(--muted); margin-bottom: .35rem; text-transform: uppercase; letter-spacing: .04em; }
input[type=text] {
  width: 100%; font: 1.15rem/1.3 "Atkinson Hyperlegible", system-ui, sans-serif;
  padding: .7rem .85rem; border-radius: 10px; border: 2px solid var(--line);
  background: var(--paper); color: var(--ink);
}
input[type=text]:focus { outline: none; border-color: var(--accent); }
.preview { min-height: 2rem; padding: .35rem .1rem; color: var(--muted); overflow-x: auto; }
.keypad { display: grid; grid-template-columns: repeat(9, 1fr); gap: .35rem; margin: .25rem 0 .5rem; }
.keypad button {
  font: 700 1.05rem "Atkinson Hyperlegible", system-ui, sans-serif; padding: .55rem 0;
  border-radius: 9px; border: 1px solid var(--line); background: var(--paper); color: var(--ink); cursor: pointer;
}
.keypad button:active { transform: scale(.96); }
.keypad .wide { font-size: .85rem; }
@media (max-width: 480px) { .keypad { grid-template-columns: repeat(5, 1fr); } }
.help { color: var(--muted); font-size: .88rem; margin: .25rem 0 0; }

.choices { display: grid; gap: .5rem; }
.choice {
  display: flex; align-items: center; gap: .75rem; text-align: left; cursor: pointer;
  border: 2px solid var(--line); border-radius: 12px; background: var(--paper); color: var(--ink);
  padding: .6rem .85rem; font: inherit; min-height: 3.2rem; overflow-x: auto;
}
.choice .letter {
  flex: none; width: 1.8rem; height: 1.8rem; border-radius: 50%; display: grid; place-items: center;
  background: var(--line); font-weight: 700; font-size: .9rem;
}
.choice.selected { border-color: var(--accent); background: var(--accent-soft); }
.choice.selected .letter { background: var(--accent); color: var(--accent-ink); }
.choice.right { border-color: var(--good); background: var(--good-soft); }
.choice.wrong { border-color: var(--bad); background: var(--bad-soft); }

.actions { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: .9rem; }
.btn {
  font: 700 1rem "Atkinson Hyperlegible", system-ui, sans-serif; cursor: pointer;
  border-radius: 10px; padding: .65rem 1.1rem; border: 2px solid transparent;
}
.btn.primary { background: var(--accent); color: var(--accent-ink); }
.btn.primary:hover { filter: brightness(1.06); }
.btn.ghost { background: transparent; border-color: var(--line); color: var(--ink); }
.btn.big { font-size: 1.08rem; padding: .8rem 1.4rem; }
.btn:disabled { opacity: .55; cursor: default; }
.linkish { background: none; border: 0; color: var(--muted); text-decoration: underline; cursor: pointer; font: inherit; font-size: .9rem; }

.hint { margin-top: .9rem; background: var(--warn-soft); border-radius: 10px; padding: .7rem .9rem; }
.hint::before { content: "Hint  "; font-weight: 700; }
.error { color: var(--bad); font-weight: 700; margin: .75rem 0 0; }

.verdict { font: 700 1.25rem "Fraunces", Georgia, serif; margin-bottom: .5rem; }
.verdict.good { color: var(--good); }
.verdict.bad { color: var(--bad); }
.entries { list-style: none; padding: 0; margin: 0; display: flex; flex-wrap: wrap; gap: .45rem; }
.entries li { border-radius: 10px; padding: .35rem .7rem; font-size: 1rem; }
.entries li.ok { background: var(--good-soft); }
.entries li.no { background: var(--bad-soft); }
.entries li .note { display: block; font-size: .8rem; color: var(--muted); }
.entries li.ok::before { content: "✓ "; color: var(--good); font-weight: 700; }
.entries li.no::before { content: "✗ "; color: var(--bad); font-weight: 700; }
.notes { margin: .6rem 0 0; padding-left: 1.1rem; color: var(--muted); }

.answerbox { border-left: 5px solid var(--accent); }
.answerbox > div { font-size: 1.15rem; overflow-x: auto; }
.steps { padding-left: 0; list-style: none; counter-reset: step; margin: 0; }
.steps li {
  counter-increment: step; position: relative; padding: .55rem 0 .55rem 2.4rem;
  border-bottom: 1px solid var(--line);
}
.steps li:last-child { border-bottom: 0; }
.steps li::before {
  content: counter(step); position: absolute; left: 0; top: .6rem;
  width: 1.7rem; height: 1.7rem; border-radius: 50%; display: grid; place-items: center;
  background: var(--accent-soft); color: var(--accent); font-weight: 700; font-size: .85rem;
}
.steps li.sub::before { content: ""; background: transparent; border: 2px solid var(--accent-soft); }
.steps li.head { padding-top: .9rem; }
.steps li.head::before { content: "→"; background: var(--accent); color: var(--accent-ink); }
.steps .m { overflow-x: auto; overflow-y: hidden; }
.steps .katex-display { margin: .45rem 0 .1rem; text-align: left; }
.steps .katex-display > .katex { text-align: left; }
.takeaway { background: var(--accent-soft); border-color: transparent; }
.takeaway p { margin: 0; }
.small { font-size: .9rem; color: var(--muted); }
canvas#graph { width: 100%; display: block; border-radius: 10px; background: var(--paper); }
.sticky { position: sticky; bottom: .75rem; justify-content: center; }

/* ---- Ask the coach ---- */
.modes { display: flex; gap: .4rem; margin-bottom: .75rem; }
.mode {
  flex: 1; font: 700 1rem "Atkinson Hyperlegible", system-ui, sans-serif; cursor: pointer;
  padding: .6rem .5rem; border-radius: 10px; border: 2px solid var(--line);
  background: transparent; color: var(--ink);
}
.mode.active { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.working { color: var(--muted); font-weight: 700; margin: 0 0 1rem; }
.readcard .display { overflow-x: auto; }
.readdomain { overflow-x: auto; color: var(--muted); }
.assumptions { margin: .6rem 0 0; padding-left: 1.1rem; color: var(--muted); font-size: .92rem; }
.badge {
  display: inline-block; font-weight: 700; font-size: .85rem; padding: .25rem .65rem;
  border-radius: 999px; margin-bottom: .6rem; cursor: help;
}
.badge.verified { background: var(--good-soft); color: var(--good); }
.badge.unverified { background: var(--warn-soft); color: #8a5a00; }
.badge.failed { background: var(--bad-soft); color: var(--bad); }
@media (prefers-color-scheme: dark) { .badge.unverified { color: #f2c46b; } }
canvas#askGraph { width: 100%; display: block; border-radius: 10px; background: var(--paper); }
@media (max-width: 480px) { #ask .actions .btn { flex: 1 1 auto; } }

/* ---- Ask: photo input ---- */
.photorow { display: flex; align-items: center; gap: .6rem; margin-top: .75rem; }
.photothumb { width: 56px; height: 56px; object-fit: cover; border-radius: 8px; border: 1px solid var(--line); background: var(--paper); }
.photoremove {
  width: 2.2rem; height: 2.2rem; border-radius: 50%; border: 1px solid var(--line);
  background: var(--paper); color: var(--ink); font-size: 1.3rem; line-height: 1; cursor: pointer; margin-left: auto;
}
.candidates { display: grid; gap: .5rem; margin-top: .6rem; }
.candidate {
  display: block; width: 100%; text-align: left; cursor: pointer; font: inherit;
  border: 2px solid var(--line); border-radius: 12px; background: var(--paper); color: var(--ink);
  padding: .65rem .85rem; min-height: 3.2rem;
}
.candidate:hover, .candidate:focus-visible { border-color: var(--accent); outline: none; }
.candidate .csource { display: block; font-weight: 700; }
.candidate .cmath { display: block; overflow-x: auto; padding: .15rem 0; }
.candidate .cdomain { display: block; overflow-x: auto; font-size: .85rem; color: var(--muted); }
.readsource { margin: 0 0 .25rem; font-size: .88rem; font-weight: 700; color: var(--muted); }
.backrow { margin: .6rem 0 0; }

/* ---- Ask: per-step "why?" ---- */
.why {
  display: inline-block; margin-top: .35rem; font: 700 .9rem "Atkinson Hyperlegible", system-ui, sans-serif;
  color: var(--accent); background: transparent; border: 1px solid var(--line); border-radius: 999px;
  padding: .35rem .85rem; min-height: 2.2rem; cursor: pointer;
}
.why:hover, .why:focus-visible { border-color: var(--accent); outline: none; }
.why[aria-expanded="true"] { background: var(--accent-soft); border-color: transparent; }
.why:disabled { opacity: .7; cursor: default; }
.why-panel { margin-top: .5rem; background: var(--paper); border-left: 3px solid var(--accent-soft); border-radius: 8px; padding: .6rem .8rem; font-size: .94rem; }
.why-head { font-size: .8rem; font-weight: 700; color: var(--muted); text-transform: uppercase; letter-spacing: .04em; margin-bottom: .2rem; }
.why-body { overflow-x: auto; }
.why-err { color: var(--bad); font-weight: 700; }