:root {
  --bg: #FAF9F5;
  --surface: #FFFFFF;
  --surface-2: #F1EFE8;
  --text: #2C2C2A;
  --text-2: #5F5E5A;
  --text-3: #888780;
  --border: #D8D6CC;
  --border-strong: #B4B2A9;
  --accent: #534AB7;
  --ok-bg: #EAF3DE;
  --ok-fg: #3B6D11;
  --ok-br: #97C459;
  --no-bg: #FCEBEB;
  --no-fg: #A32D2D;
  --no-br: #F09595;
  --radius: 10px;
  --sans: "Inter", "Segoe UI", system-ui, -apple-system, sans-serif;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #1B1B19;
    --surface: #262624;
    --surface-2: #2F2F2C;
    --text: #EDEBE3;
    --text-2: #B4B2A9;
    --text-3: #888780;
    --border: #3D3D3A;
    --border-strong: #55554F;
    --accent: #AFA9EC;
    --ok-bg: #27500A;
    --ok-fg: #C0DD97;
    --ok-br: #639922;
    --no-bg: #791F1F;
    --no-fg: #F7C1C1;
    --no-br: #E24B4A;
  }
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.65;
  -webkit-text-size-adjust: 100%;
}

.wrap { max-width: 780px; margin: 0 auto; padding: 0 20px; }

h1, h2, h3 { font-weight: 600; line-height: 1.25; margin: 0 0 12px; }
h1 { font-size: 34px; letter-spacing: -0.02em; }
h2 { font-size: 24px; margin-top: 56px; }
h3 { font-size: 19px; }
p { margin: 0 0 14px; }
ul { margin: 0; padding-left: 22px; }
li { margin-bottom: 8px; }

.site-head {
  padding: 48px 0 32px;
  border-bottom: 1px solid var(--border);
  background: var(--surface);
}
.eyebrow {
  font-size: 13px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-3);
  margin-bottom: 8px;
}
.lead { color: var(--text-2); font-size: 18px; margin-bottom: 20px; }

.nav { display: flex; flex-wrap: wrap; gap: 8px; }
.nav a {
  display: inline-block;
  padding: 7px 14px;
  border: 1px solid var(--border);
  border-radius: 999px;
  color: var(--text);
  text-decoration: none;
  font-size: 15px;
}
.nav a:hover { border-color: var(--border-strong); background: var(--surface-2); }

main { padding-bottom: 72px; }

.card {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 22px;
  margin-bottom: 20px;
}
.card > :last-child { margin-bottom: 0; }

.fig { overflow-x: auto; margin-top: 18px; padding-bottom: 4px; }
.fig svg { display: block; width: 100%; min-width: 600px; height: auto; }

.t  { font: 400 14px var(--sans); fill: var(--text); }
.th { font: 500 14px var(--sans); fill: var(--text); }
.ts { font: 400 12px var(--sans); fill: var(--text-2); }
.box { fill: var(--surface-2); stroke: var(--border-strong); stroke-width: 0.5; }
.ink { stroke: #888780; stroke-width: 1.5; }
.solid { fill: #888780; }
.wire { stroke: #888780; stroke-width: 1.5; }
.pull { stroke: #1D9E75; stroke-width: 1.5; }

.c-purple rect, .c-purple circle, .c-purple ellipse { fill: #EEEDFE; stroke: #534AB7; stroke-width: 0.5; }
.c-purple .th, .c-purple .t { fill: #3C3489; }
.c-purple .ts { fill: #534AB7; }
.c-teal rect, .c-teal circle, .c-teal ellipse { fill: #E1F5EE; stroke: #0F6E56; stroke-width: 0.5; }
.c-teal .th, .c-teal .t { fill: #085041; }
.c-teal .ts { fill: #0F6E56; }
.c-gray rect, .c-gray circle, .c-gray ellipse { fill: #F1EFE8; stroke: #5F5E5A; stroke-width: 0.5; }
.c-gray .th, .c-gray .t { fill: #2C2C2A; }
.c-gray .ts { fill: #5F5E5A; }
rect.c-gray-s, circle.c-gray-s { fill: #F1EFE8; stroke: #5F5E5A; stroke-width: 0.5; }

@media (prefers-color-scheme: dark) {
  .c-purple rect, .c-purple circle, .c-purple ellipse { fill: #3C3489; stroke: #AFA9EC; }
  .c-purple .th, .c-purple .t { fill: #CECBF6; }
  .c-purple .ts { fill: #AFA9EC; }
  .c-teal rect, .c-teal circle, .c-teal ellipse { fill: #085041; stroke: #5DCAA5; }
  .c-teal .th, .c-teal .t { fill: #9FE1CB; }
  .c-teal .ts { fill: #5DCAA5; }
  .c-gray rect, .c-gray circle, .c-gray ellipse { fill: #444441; stroke: #B4B2A9; }
  .c-gray .th, .c-gray .t { fill: #F1EFE8; }
  .c-gray .ts { fill: #D3D1C7; }
  rect.c-gray-s, circle.c-gray-s { fill: #444441; stroke: #B4B2A9; }
  .ink, .wire { stroke: #B4B2A9; }
  .solid { fill: #B4B2A9; }
  .pull { stroke: #5DCAA5; }
}

.modes { display: flex; flex-wrap: wrap; gap: 8px; margin-bottom: 16px; }
.mode {
  font: 500 15px var(--sans);
  padding: 9px 16px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--surface);
  color: var(--text-2);
  cursor: pointer;
}
.mode:hover { border-color: var(--border-strong); }
.mode.is-active {
  background: var(--accent);
  border-color: var(--accent);
  color: #FFFFFF;
}
@media (prefers-color-scheme: dark) { .mode.is-active { color: #26215C; } }

.quiz-top { display: flex; justify-content: space-between; gap: 12px; }
.counter, .score { font-size: 14px; color: var(--text-2); margin: 0; }

.bar { height: 4px; background: var(--surface-2); border-radius: 999px; margin: 12px 0 22px; overflow: hidden; }
.bar span { display: block; height: 100%; width: 0; background: var(--accent); transition: width .25s ease; }

.prompt { font-size: 15px; color: var(--text-2); margin-bottom: 6px; }
.term { font-size: 30px; font-weight: 600; letter-spacing: -0.01em; margin: 0 0 22px; }

.answers { display: grid; gap: 10px; }
.ans {
  font: 400 17px var(--sans);
  text-align: left;
  padding: 14px 16px;
  border-radius: var(--radius);
  border: 1px solid var(--border);
  background: var(--surface-2);
  color: var(--text);
  cursor: pointer;
  display: flex;
  align-items: center;
  gap: 12px;
}
.ans:hover:not(:disabled) { border-color: var(--border-strong); }
.ans:disabled { cursor: default; }
.ans .key {
  flex: none;
  width: 24px; height: 24px;
  border-radius: 6px;
  border: 1px solid var(--border-strong);
  font-size: 13px;
  display: grid; place-items: center;
  color: var(--text-3);
}
.ans.correct { background: var(--ok-bg); border-color: var(--ok-br); color: var(--ok-fg); }
.ans.correct .key { border-color: var(--ok-br); color: var(--ok-fg); }
.ans.wrong { background: var(--no-bg); border-color: var(--no-br); color: var(--no-fg); }
.ans.wrong .key { border-color: var(--no-br); color: var(--no-fg); }

.feedback { margin-top: 16px; font-size: 16px; }
.feedback:empty { margin-top: 0; }
.feedback .verdict { font-weight: 600; margin-bottom: 4px; }
.feedback.ok .verdict { color: var(--ok-fg); }
.feedback.no .verdict { color: var(--no-fg); }
.feedback p { margin: 0; color: var(--text-2); }

.quiz-foot { display: flex; gap: 10px; margin-top: 22px; }
.btn {
  font: 500 16px var(--sans);
  padding: 11px 22px;
  border-radius: var(--radius);
  border: 1px solid transparent;
  cursor: pointer;
}
.btn.primary { background: var(--accent); color: #FFFFFF; }
@media (prefers-color-scheme: dark) { .btn.primary { color: #26215C; } }
.btn.ghost { background: transparent; border-color: var(--border); color: var(--text-2); }
.btn.ghost:hover { border-color: var(--border-strong); }

.result .big { font-size: 30px; font-weight: 600; margin-bottom: 6px; }
.mistake {
  border-top: 1px solid var(--border);
  padding: 12px 0;
  font-size: 15px;
}
.mistake b { font-weight: 600; }
.mistake span { color: var(--text-2); }

.cheat { display: grid; gap: 14px; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); margin-bottom: 20px; }
.cheat-item {
  background: var(--surface);
  border: 1px solid var(--border);
  border-radius: 14px;
  padding: 18px;
}
.cheat-item p { font-size: 15px; color: var(--text-2); }
.cheat-item .ex { color: var(--text-3); font-size: 14px; margin-bottom: 0; }

.site-foot {
  border-top: 1px solid var(--border);
  padding: 24px 0 40px;
  color: var(--text-3);
  font-size: 14px;
}
.site-foot p { margin: 0; }

:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

@media (max-width: 520px) {
  h1 { font-size: 27px; }
  .term { font-size: 24px; }
  .card { padding: 18px; }
}