:root {
  --bg: #f4f5f7;
  --card: #ffffff;
  --ink: #1f2328;
  --muted: #6b7280;
  --line: #e3e5e8;
  --accent: #1f9e96;
  --good: #1e8e3e;
  --warn: #c76a00;
  --bad: #d93025;
  --teacher: #1a73e8;
  --shadow: 0 2px 10px rgba(20, 24, 31, 0.06);
  color-scheme: light dark;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #15171a;
    --card: #1f2226;
    --ink: #e8eaed;
    --muted: #9aa0a6;
    --line: #33373c;
    --good: #5bb974;
    --warn: #f0a24b;
    --bad: #f28b82;
    --teacher: #8ab4f8;
    --shadow: none;
  }
}
* { box-sizing: border-box; }
html, body { margin: 0; }
body {
  background: var(--bg);
  color: var(--ink);
  font: 15px/1.4 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
}
[hidden] { display: none !important; }
h1, h2, h3, h4, h5 { margin: 0 0 8px; line-height: 1.2; }
h2 { font-size: 22px; }
h3 { font-size: 17px; }
h4 { font-size: 15px; }
h5 { font-size: 13px; margin-top: 8px; }
code { background: rgba(127, 127, 127, 0.15); padding: 1px 5px; border-radius: 4px; word-break: break-all; }
button, select, input { font: inherit; color: inherit; }
button {
  cursor: pointer;
  border: 1px solid var(--line);
  background: var(--card);
  border-radius: 8px;
  padding: 7px 12px;
}
button:disabled { opacity: 0.45; cursor: default; }
button.primary { background: var(--accent); border-color: var(--accent); color: #fff; font-weight: 600; }
button.link { border: none; background: none; color: var(--accent); padding: 4px 6px; }
input[type=email], input[type=password], input[type=search], select {
  border: 1px solid var(--line);
  background: var(--card);
  border-radius: 8px;
  padding: 8px 10px;
  width: 100%;
}
.muted { color: var(--muted); }
.small { font-size: 12.5px; }
.center { text-align: center; }
.num { font-variant-numeric: tabular-nums; }
.good { color: var(--good); }
.warn { color: var(--warn); }
.bad { color: var(--bad); }
.teal { color: var(--accent); }
.teacher { color: var(--teacher); }
.spacer { flex: 1; }
.card { background: var(--card); border: 1px solid var(--line); border-radius: 14px; box-shadow: var(--shadow); padding: 14px 16px; }
.message { min-height: 1.4em; margin: 6px 0 0; }
.message.error { color: var(--bad); }

/* sign-in */
.signin { min-height: 100vh; display: grid; place-items: center; padding: 16px; }
.signin-card { width: min(380px, 100%); display: grid; gap: 12px; }
.signin-card label { display: grid; gap: 4px; font-weight: 500; }

/* top bar */
.topbar {
  position: sticky; top: 0; z-index: 5;
  display: flex; align-items: center; gap: 12px; flex-wrap: wrap;
  padding: 10px 16px;
  background: var(--card);
  border-bottom: 1px solid var(--line);
}
.brand { font-weight: 700; }
#student { width: auto; min-width: 180px; font-weight: 600; }
.tabs { display: flex; gap: 4px; flex-wrap: wrap; }
.tabs button { border: none; background: none; padding: 7px 10px; border-radius: 8px; color: var(--muted); }
.tabs button[aria-selected=true] { background: color-mix(in srgb, var(--accent) 14%, transparent); color: var(--ink); font-weight: 600; }
.env { background: #fbbc04; color: #000; font-weight: 700; font-size: 12px; padding: 3px 8px; border-radius: 6px; }
.toast {
  position: fixed; left: 50%; bottom: 84px; transform: translateX(-50%); z-index: 20;
  background: var(--ink); color: var(--bg); padding: 10px 16px; border-radius: 10px; margin: 0;
  max-width: calc(100vw - 32px);
}
.toast.error { background: var(--bad); color: #fff; }
.view { padding: 16px; padding-bottom: 96px; }
.empty { text-align: center; padding: 60px 16px; }

/* Assign Words */
.words-head { display: flex; align-items: center; gap: 12px; flex-wrap: wrap; margin-bottom: 12px; }
.words-head h2 { margin: 0; flex: 1; }
.columns { display: flex; gap: 14px; overflow-x: auto; padding-bottom: 8px; align-items: stretch; }
.column {
  flex: 0 0 240px;
  display: flex; flex-direction: column; gap: 8px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 16px;
  box-shadow: var(--shadow);
  padding: 12px;
  height: calc(100vh - 190px);
  min-height: 320px;
}
.column.drop { background: color-mix(in srgb, var(--cat) 15%, var(--card)); }
.column h3 { color: var(--cat); text-align: center; margin: 0; }
.column .count { font-size: 12px; color: var(--muted); font-weight: 500; }
.column-words { flex: 1; overflow-y: auto; display: flex; flex-direction: column; gap: 6px; padding: 2px; }
.chip {
  display: flex; align-items: center; gap: 6px;
  background: color-mix(in srgb, var(--cat) 13%, transparent);
  border: 2px solid transparent;
  border-radius: 10px;
  padding: 6px 8px 6px 10px;
  font-size: 17px; font-weight: 500;
  cursor: grab;
  text-align: left;
  width: 100%;
}
.chip .label { flex: 1; }
.chip .remove { border: none; background: none; color: var(--muted); padding: 0 4px; font-size: 13px; }
.chip .remove:hover { color: var(--bad); }
.chip.selectable { cursor: pointer; }
.chip.selectable.on { background: color-mix(in srgb, var(--cat) 32%, transparent); border-color: var(--cat); }
.chip .tick {
  display: inline-grid; place-items: center;
  width: 20px; height: 20px; border-radius: 50%;
  border: 2px solid var(--muted); font-size: 12px; color: #fff; flex: 0 0 auto;
}
.chip.on .tick { background: var(--cat); border-color: var(--cat); }
.column .add { background: var(--cat); border-color: var(--cat); color: #fff; font-weight: 600; }
.column .select-all { color: var(--cat); align-self: center; font-weight: 500; }
.bulkbar {
  position: fixed; left: 0; right: 0; bottom: 0; z-index: 10;
  display: flex; align-items: center; gap: 14px; flex-wrap: wrap;
  padding: 12px 20px;
  background: color-mix(in srgb, var(--card) 92%, transparent);
  backdrop-filter: blur(10px);
  border-top: 1px solid var(--line);
  font-size: 17px;
}
.bulkbar button { padding: 9px 16px; }
.graduate { background: #8e44ad !important; border-color: #8e44ad !important; }
.menu { position: relative; }
.menu summary {
  list-style: none; cursor: pointer;
  border: 1px solid var(--line); border-radius: 8px; padding: 9px 16px; background: var(--card);
}
.menu summary::-webkit-details-marker { display: none; }
.menu.disabled { pointer-events: none; opacity: 0.45; }
.menu-items {
  position: absolute; bottom: calc(100% + 6px); right: 0; min-width: 200px;
  display: grid; background: var(--card); border: 1px solid var(--line); border-radius: 12px;
  box-shadow: 0 8px 30px rgba(0, 0, 0, 0.18); padding: 6px;
}
.menu-items button { border: none; text-align: left; border-radius: 8px; }
.menu-items button:hover { background: color-mix(in srgb, var(--cat) 15%, transparent); }

/* bank dialog */
dialog { border: none; border-radius: 16px; padding: 0; width: min(520px, calc(100vw - 32px)); background: var(--card); color: var(--ink); }
dialog::backdrop { background: rgba(0, 0, 0, 0.35); }
.bank { display: grid; gap: 10px; padding: 16px; max-height: min(80vh, 760px); grid-template-rows: auto auto auto 1fr; }
.bank-head { display: flex; align-items: center; justify-content: space-between; }
.bank-head h2 { margin: 0; }
.segmented { display: flex; flex-wrap: wrap; border: 1px solid var(--line); border-radius: 9px; overflow: hidden; width: fit-content; }
.segmented button { border: none; border-radius: 0; border-right: 1px solid var(--line); padding: 6px 12px; }
.segmented button:last-child { border-right: none; }
.segmented button[aria-pressed=true] { background: var(--accent); color: #fff; }
.bank-list { list-style: none; margin: 0; padding: 0; overflow-y: auto; min-height: 200px; }
.bank-list button {
  width: 100%; display: flex; align-items: center; justify-content: space-between;
  border: none; border-bottom: 1px solid var(--line); border-radius: 0; padding: 9px 6px; text-align: left;
}
.bank-list button:not(:disabled):hover { background: color-mix(in srgb, var(--accent) 10%, transparent); }
.bank-list .word { font-size: 17px; }
.bank-list .in { color: var(--good); font-size: 13px; }
.bank-list li.center { padding: 10px; }

/* sessions */
.sessions { display: grid; gap: 10px; }
.session summary { cursor: pointer; display: flex; gap: 12px; align-items: baseline; flex-wrap: wrap; }
.session .runs { flex: 1 1 100%; }
.run { margin-top: 12px; padding-top: 10px; border-top: 1px solid var(--line); }
.indent { padding-left: 14px; }
.line { display: flex; flex-wrap: wrap; align-items: baseline; gap: 6px; padding: 2px 0; }
.line-block { padding: 3px 0; border-radius: 8px; }
.judge-stt { background: color-mix(in srgb, #f08c00 12%, transparent); padding: 6px; }
.judge-rescued { background: color-mix(in srgb, #8e44ad 12%, transparent); padding: 6px; }
.judge-teacher { background: color-mix(in srgb, #1a73e8 12%, transparent); padding: 6px; }
.judge { font-size: 11px; font-weight: 700; padding: 2px 7px; border-radius: 99px; background: rgba(127, 127, 127, 0.18); }
.pf.ok { color: var(--good); }
.pf.no { color: var(--bad); }
.badge { font-size: 12px; padding: 2px 7px; border-radius: 99px; }
.badge.ok { background: color-mix(in srgb, var(--good) 15%, transparent); }
.badge.no { background: color-mix(in srgb, var(--bad) 15%, transparent); }

/* tables */
.filter { max-width: 280px; margin-bottom: 10px; }
.table { width: 100%; border-collapse: collapse; background: var(--card); border-radius: 12px; overflow: hidden; border: 1px solid var(--line); }
.table th, .table td { padding: 8px 10px; border-bottom: 1px solid var(--line); text-align: left; }
.table th { font-size: 12.5px; color: var(--muted); font-weight: 600; }
.table td.center, .table th:nth-child(n+3) { text-align: center; }

/* confidence */
.summary, .band { margin-bottom: 12px; }
.conf-row { display: flex; align-items: center; gap: 12px; padding: 7px 0; border-bottom: 1px solid var(--line); }
.conf-row > div:first-child { flex: 1; }
.conf-row:last-child { border-bottom: none; }
.big { font-size: 18px; }
.chip-band { font-size: 11.5px; font-weight: 700; padding: 2px 8px; border-radius: 99px; color: var(--band); background: color-mix(in srgb, var(--band) 16%, transparent); margin: 0 4px; }
.score { font-size: 22px; font-weight: 700; font-variant-numeric: tabular-nums; }

/* performance */
.perf-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(340px, 1fr)); gap: 12px; align-items: start; }
.metric { padding: 6px 0; border-bottom: 1px solid var(--line); }
.metric:last-child { border-bottom: none; }
.metric-top { display: flex; justify-content: space-between; gap: 8px; align-items: baseline; }

@media (max-width: 640px) {
  .topbar { gap: 8px; }
  #student { flex: 1; }
  .column { flex-basis: 210px; height: calc(100vh - 260px); }
  .perf-grid { grid-template-columns: 1fr; }
  .table th:nth-child(2), .table td:nth-child(2) { display: none; }
}