:root {
  --ink: #1f2a37;
  --muted: #5b6776;
  --line: #d5dbe3;
  --bg: #f4f6f9;
  --card: #ffffff;
  --accent: #1d5fa8;
  --accent-ink: #ffffff;
  --good: #1a7f4b;
  --good-bg: #e3f4ea;
  --bad: #b3261e;
  --bad-bg: #fbe9e7;
  --warn-bg: #fff4d6;
}
* { box-sizing: border-box; }
body {
  margin: 0;
  font: 17px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  color: var(--ink);
  background: var(--bg);
}
header.bar {
  background: var(--accent);
  color: var(--accent-ink);
  padding: 14px 20px;
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}
header.bar .brand { margin-right: auto; display: flex; align-items: center; gap: 10px; color: #fff; text-decoration: none; font-weight: 700; font-size: 1.1rem; }
header.bar .mark { background: #fff; color: var(--accent); border-radius: 8px; padding: 2px 8px; font-family: Georgia, "Times New Roman", serif; font-size: 1.05rem; }
a.onbar { color: #fff; border: 1px solid #fff; border-radius: 8px; padding: 5px 14px; text-decoration: none; font-weight: 600; font-size: 0.95rem; }
a.onbar:hover, button.onbar:hover { background: rgba(255, 255, 255, 0.16); }
html, body { min-height: 100%; }
body { display: flex; flex-direction: column; min-height: 100vh; }
main { flex: 1; width: 100%; }
header.bar .who { font-size: 0.95rem; display: flex; gap: 12px; align-items: center; }
main { max-width: 760px; margin: 0 auto; padding: 24px 16px 64px; }
main.wide { max-width: 1200px; }
.card {
  box-shadow: 0 1px 3px rgba(31, 42, 55, 0.06);
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 20px;
  margin-bottom: 20px;
}
h2 { font-size: 1.25rem; margin: 0 0 12px; }
h3 { font-size: 1.05rem; margin: 20px 0 8px; }
p { margin: 0 0 12px; }
.muted { color: var(--muted); }
.error { color: var(--bad); font-weight: 600; min-height: 1.5em; }
label { display: block; font-weight: 600; margin-bottom: 6px; }
input[type="text"], input[type="password"], select, textarea {
  width: 100%;
  font: inherit;
  padding: 10px 12px;
  border: 1px solid #9aa5b3;
  border-radius: 8px;
  background: #fff;
  color: var(--ink);
  margin-bottom: 14px;
}
button {
  font: inherit;
  font-weight: 600;
  padding: 10px 18px;
  border-radius: 8px;
  border: 1px solid var(--accent);
  background: var(--accent);
  color: var(--accent-ink);
  cursor: pointer;
}
button.plain { background: #fff; color: var(--accent); }
button.small { padding: 4px 10px; font-size: 0.85rem; }
button.onbar { background: transparent; border-color: #fff; color: #fff; padding: 4px 12px; }
button:disabled { opacity: 0.5; cursor: default; }
button:focus-visible, input:focus-visible, select:focus-visible, textarea:focus-visible, a:focus-visible {
  outline: 3px solid #f2a900;
  outline-offset: 2px;
}

/* student: lesson list */
.lessons { display: grid; grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 12px; }
.lesson {
  text-align: left;
  background: #fff;
  color: var(--ink);
  border: 1px solid var(--line);
  padding: 14px 16px;
}
.lesson:hover { border-color: var(--accent); background: #f3f8fe; }
.lesson strong { display: block; font-size: 1.05rem; }
.lesson span { font-weight: 400; color: var(--muted); font-size: 0.92rem; }

/* student: quiz */
fieldset.question { border: 1px solid var(--line); border-radius: 10px; background: #fff; padding: 16px 20px; margin: 0 0 16px; }
fieldset.question legend { font-weight: 600; padding: 0 6px; color: var(--muted); font-size: 0.9rem; }
.definition { font-size: 1.1rem; margin-bottom: 12px; }
.choices { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; }
@media (max-width: 520px) { .choices { grid-template-columns: 1fr; } }
.choice { display: flex; align-items: center; gap: 10px; border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px; font-weight: 400; margin: 0; cursor: pointer; }
.choice:has(input:checked) { border-color: var(--accent); background: #e8f0fa; }
.choice input { width: 18px; height: 18px; margin: 0; }
.score { font-size: 2rem; font-weight: 700; margin: 0 0 4px; }
.review-row { border-left: 5px solid var(--good); background: var(--good-bg); padding: 10px 14px; border-radius: 6px; margin-bottom: 8px; }
.review-row.wrong { border-color: var(--bad); background: var(--bad-bg); }

/* teacher */
.toolbar { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; margin-bottom: 12px; }
.scroll { overflow-x: auto; }
table { border-collapse: collapse; width: 100%; font-size: 0.92rem; }
th, td { border: 1px solid var(--line); padding: 6px 8px; text-align: center; white-space: nowrap; }
th.name, td.name { text-align: left; position: sticky; left: 0; background: #fff; }
thead th { background: #eef1f5; }
thead th.name { background: #eef1f5; }
td.cell-high { background: var(--good-bg); }
td.cell-mid { background: var(--warn-bg); }
td.cell-low { background: var(--bad-bg); }
td.left, th.left { text-align: left; white-space: normal; }
td input.inline, td select.inline { margin: 0; padding: 4px 8px; min-width: 150px; }
td select.inline { width: auto; }
button.danger { color: var(--bad); border-color: var(--bad); }
.wrong-choices { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; }
@media (max-width: 520px) { .wrong-choices { grid-template-columns: 1fr; } }
.lesson-toggles { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 6px; }
.lesson-toggles label { font-weight: 400; display: flex; gap: 8px; align-items: center; margin: 0; }
.tabs { display: flex; gap: 6px; margin-bottom: 16px; flex-wrap: wrap; }
.tabs button[aria-selected="true"] { background: var(--accent); color: #fff; }
.tabs button { background: #fff; color: var(--accent); }
a { color: var(--accent); }
.hidden { display: none !important; }