:root {
  --bg: #f6f7f9;
  --card: #ffffff;
  --ink: #1d2433;
  --muted: #6b7385;
  --navy: #1f2a5c;
  --blue: #2f6fc9;
  --blue-soft: #e8f0fb;
  --green: #2e9e5b;
  --green-soft: #e7f5ec;
  --red: #c8423b;
  --red-soft: #fbeceb;
  --amber: #c98a1b;
  --border: #e3e6ec;
  --m1: #d2e7f9; --m2: #a5cff3; --m3: #78b6ed; --m4: #4a9ee8; --m5: #1d86e2; --m6: #176bb5;
  --radius: 10px;
  --shadow: 0 1px 2px rgba(20, 30, 60, .06), 0 2px 8px rgba(20, 30, 60, .04);
}
* { box-sizing: border-box; }
html, body { margin: 0; background: var(--bg); color: var(--ink);
  font: 16px/1.55 -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif; }
a { color: var(--blue); text-decoration: none; }
button { font: inherit; cursor: pointer; }
.hidden { display: none !important; }

/* top bar */
#topbar { background: #fff; border-bottom: 1px solid var(--border); position: sticky; top: 0; z-index: 10; }
.bar { max-width: 1080px; margin: 0 auto; display: flex; align-items: center; gap: 28px; padding: 0 16px; height: 56px; }
.logo { font-weight: 700; letter-spacing: .14em; color: var(--navy); font-size: 14px; }
.logo-mark { color: var(--blue); font-size: 18px; }
nav a { color: var(--muted); font-size: 13px; letter-spacing: .1em; text-transform: uppercase; padding: 18px 2px; border-bottom: 3px solid transparent; }
nav a.active { color: var(--blue); border-bottom-color: var(--blue); }
nav { display: flex; gap: 24px; }
.spacer { flex: 1; }
.avatar { width: 34px; height: 34px; border-radius: 50%; border: 1px solid var(--border); background: var(--bg); color: var(--navy); font-weight: 600; font-size: 13px; }

main { max-width: 1080px; margin: 0 auto; padding: 24px 16px 80px; }

/* cards & layout */
.card { background: var(--card); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); }
.pad { padding: 18px 20px; }
.grid { display: grid; grid-template-columns: 320px 1fr; gap: 24px; align-items: start; }
@media (max-width: 820px) { .grid { grid-template-columns: 1fr; } }
.stack > * + * { margin-top: 16px; }
.caps { font-size: 12px; letter-spacing: .1em; text-transform: uppercase; color: var(--muted); }
.big { font-size: 28px; font-weight: 700; color: var(--navy); }
.muted { color: var(--muted); }
.small { font-size: 13px; }
h1, h2, h3 { color: var(--navy); line-height: 1.25; }
h1 { font-size: 26px; margin: 0 0 6px; }
h2 { font-size: 20px; margin: 0 0 8px; }
h3 { font-size: 16px; margin: 0 0 6px; }

.btn { border: 0; background: var(--blue); color: #fff; padding: 10px 22px; border-radius: 999px; font-weight: 600; font-size: 15px; }
.btn:hover { filter: brightness(1.06); }
.btn:disabled { background: #c9cfdb; cursor: default; }
.btn.ghost { background: #fff; color: var(--ink); border: 1px solid var(--border); }
.btn.small { padding: 6px 14px; font-size: 13px; }
.linkbtn { background: none; border: 0; color: var(--blue); padding: 0; font-size: 14px; }

/* login */
.login { max-width: 420px; margin: 10vh auto; text-align: center; }
.login input { width: 100%; padding: 12px 14px; border-radius: 8px; border: 1px solid var(--border); font-size: 16px; margin: 14px 0; }
.profiles { display: flex; flex-wrap: wrap; gap: 8px; justify-content: center; margin-top: 10px; }

/* course card */
.course-card { display: flex; justify-content: space-between; align-items: center; gap: 12px; }
.course-card h3 { font-size: 14px; letter-spacing: .06em; text-transform: uppercase; }
.pct { width: 58px; height: 58px; border-radius: 50%; display: grid; place-items: center; font-weight: 700; color: var(--navy); flex: none; }

/* xp */
.goalbar { height: 10px; background: #edf0f5; border-radius: 99px; overflow: hidden; }
.goalbar > div { height: 100%; background: var(--blue); border-radius: 99px; transition: width .4s; }
.week { display: flex; align-items: flex-end; gap: 8px; height: 90px; margin-top: 10px; }
.week .col { flex: 1; display: flex; flex-direction: column; align-items: center; gap: 4px; height: 100%; justify-content: flex-end; }
.week .b { width: 100%; background: var(--m2); border-radius: 4px 4px 0 0; min-height: 2px; }
.week .col.today .b { background: var(--blue); }
.week .d { font-size: 11px; color: var(--muted); }
.streak { font-weight: 600; color: var(--amber); }

/* task cards */
.task { display: flex; gap: 14px; align-items: center; padding: 16px 18px; }
.task + .task { border-top: 1px solid var(--border); }
.task .icon { width: 38px; height: 38px; border-radius: 9px; display: grid; place-items: center; font-size: 18px; flex: none; }
.task .meta { flex: 1; min-width: 0; }
.task .kind { font-weight: 600; color: var(--navy); font-size: 14px; }
.task .tname { font-size: 15px; }
.task .tag { font-size: 11px; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); }
.task .xpv { font-size: 13px; color: var(--muted); white-space: nowrap; }
.i-lesson { background: var(--blue-soft); color: var(--blue); }
.i-review { background: #eef3e8; color: #4b8a2e; }
.i-quiz { background: #fdf3e2; color: var(--amber); }
.i-probe { background: #f1ebfb; color: #7a4fc4; }
.i-remedial { background: var(--red-soft); color: var(--red); }

.history h4 { text-align: center; color: var(--muted); font-weight: 500; margin: 22px 0 10px; font-size: 14px; }
.hist { display: flex; align-items: center; gap: 12px; padding: 12px 18px; }
.hist + .hist { border-top: 1px solid var(--border); }
.hist .ok { color: var(--green); } .hist .bad { color: var(--red); }
.xpg { font-weight: 700; } .xpg.pos { color: var(--green); } .xpg.neg { color: var(--red); }

/* course progress */
.unit { margin-bottom: 12px; }
.unit-h { display: flex; align-items: center; gap: 12px; padding: 14px 18px; cursor: pointer; }
.unit-h .n { color: var(--muted); width: 24px; }
.unit-h .name { flex: 1; font-weight: 600; color: var(--navy); }
.mbar { display: flex; height: 5px; border-radius: 3px; overflow: hidden; background: #eef1f5; margin: 0 18px 14px; }
.unit-body { padding: 0 18px 14px; }
.module-name { font-weight: 600; margin: 12px 0 6px; color: var(--ink); font-size: 14px; }
.trow { display: flex; align-items: center; gap: 12px; padding: 5px 0; font-size: 15px; }
.trow .num { color: var(--muted); width: 48px; font-size: 13px; }
.circle { width: 12px; height: 12px; border-radius: 50%; border: 1px solid #ccd2dc; flex: none; }
.lv1 { background: var(--m1); border-color: var(--m1); } .lv2 { background: var(--m2); border-color: var(--m2); }
.lv3 { background: var(--m3); border-color: var(--m3); } .lv4 { background: var(--m4); border-color: var(--m4); }
.lv5 { background: var(--m5); border-color: var(--m5); } .lv6 { background: var(--m6); border-color: var(--m6); }
.badge { font-size: 11px; padding: 1px 7px; border-radius: 99px; background: #f3eefc; color: #7a4fc4; }
.legend { display: flex; gap: 14px; flex-wrap: wrap; font-size: 12px; color: var(--muted); align-items: center; }
.legend span { display: inline-flex; align-items: center; gap: 5px; }

/* player */
.player { max-width: 820px; margin: 0 auto; }
.player-top { display: flex; align-items: center; gap: 14px; margin-bottom: 16px; }
.player-top .title { flex: 1; }
.close { background: none; border: 0; font-size: 26px; color: var(--muted); line-height: 1; }
.kps { display: flex; gap: 6px; margin-top: 6px; }
.kps i { width: 28px; height: 6px; border-radius: 3px; background: #e5e9f0; display: block; }
.kps i.done { background: var(--green); } .kps i.cur { background: var(--blue); }
.slide { padding: 26px 30px; }
.slide + .slide { margin-top: 16px; }
.slide h2 { margin-top: 0; }
.prompt { font-size: 17px; }
.step { margin: 14px 0; }
.step .lab { font-weight: 600; color: var(--navy); font-size: 14px; letter-spacing: .01em; }
.step .lab::before { content: "▸ "; color: var(--blue); }
.explain { background: var(--blue-soft); border-radius: 8px; padding: 10px 14px; margin: 10px 0 16px; font-size: 15px; }
.banner { border-radius: 8px; padding: 10px 14px; margin-bottom: 14px; font-size: 15px; }
.banner.challenge { background: #f1ebfb; color: #4d2f86; }
.banner.quiz { background: #fdf3e2; color: #7a5410; display: flex; justify-content: space-between; }
.timer { font-variant-numeric: tabular-nums; font-weight: 700; }
.timer.low { color: var(--red); }
.answers { margin: 18px 0 6px; display: flex; flex-direction: column; gap: 14px; }
.blank { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.blank input.cell, .grid-in input { padding: 8px 10px; font-size: 16px; border: 1px solid #cdd3de; border-radius: 6px; width: 120px; text-align: center; }
.grid-in { display: inline-grid; gap: 6px; padding: 6px 10px; border-left: 2px solid var(--ink); border-right: 2px solid var(--ink); border-radius: 6px; }
.grid-in input { width: 70px; }
input:focus { outline: 2px solid var(--blue-soft); border-color: var(--blue); }
.choices { display: flex; flex-direction: column; gap: 8px; }
.choice { display: flex; align-items: center; gap: 12px; padding: 10px 12px; border: 1px solid var(--border); border-radius: 8px; cursor: pointer; background: #fff; text-align: left; }
.choice:hover { border-color: #b8c4d8; }
.choice .letter { width: 30px; height: 30px; border-radius: 50%; border: 1px solid #cdd3de; display: grid; place-items: center; font-size: 14px; flex: none; }
.choice.sel { border-color: var(--navy); }
.choice.sel .letter { background: #404040; color: #fff; border-color: #404040; }
.actions { display: flex; gap: 12px; align-items: center; margin-top: 18px; flex-wrap: wrap; }
.actions .spacer { flex: 1; }
.verdict { font-weight: 600; font-size: 17px; display: flex; align-items: center; gap: 8px; margin: 6px 0 14px; }
.verdict.ok { color: var(--green); } .verdict.bad { color: var(--red); }
.answer-box { background: var(--bg); border-radius: 8px; padding: 10px 14px; margin: 10px 0; }
.err { color: var(--red); font-size: 14px; }
.diagram { display: block; margin: 12px auto; background: #fff; }
.diagram .grid { stroke: #eef0f4; stroke-width: 1; }
.diagram .axis { stroke: #9aa3b5; stroke-width: 1.2; }
.diagram .vlabel { font: italic 13px Georgia, serif; }
.refpanel { margin-top: 14px; border-top: 1px dashed var(--border); padding-top: 14px; }
.summary-xp { font-size: 40px; font-weight: 800; }
.qrow { border-top: 1px solid var(--border); padding: 14px 0; }
.note { font-size: 13px; color: var(--muted); }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 2px 0; }
textarea { width: 100%; min-height: 90px; font: inherit; padding: 10px; border-radius: 8px; border: 1px solid var(--border); }

/* modal */
.modal-bg { position: fixed; inset: 0; background: rgba(15, 20, 35, .35); display: grid; place-items: center; z-index: 50; padding: 16px; }
.modal { width: min(460px, 100%); padding: 22px 24px; }
.modal label { display: block; margin: 12px 0 4px; font-size: 14px; color: var(--muted); }
.modal input[type=number] { width: 120px; padding: 8px; border: 1px solid var(--border); border-radius: 6px; font-size: 15px; }

/* knowledge graph */
main.full { max-width: none; padding: 0; }
.kg { position: relative; height: calc(100vh - 56px); overflow: hidden; background:
  radial-gradient(circle, #e3e7ee 1px, transparent 1px) 0 0 / 22px 22px, #f8f9fb; }
.kg canvas { display: block; touch-action: none; }
.kg-tools { position: absolute; top: 14px; left: 14px; display: flex; gap: 6px; align-items: center; padding: 6px; flex-wrap: wrap; max-width: calc(100% - 28px); }
.kg-tools button { border: 1px solid var(--border); background: #fff; border-radius: 8px; padding: 6px 10px; font-size: 14px; color: var(--ink); }
.kg-tools button.on { background: var(--navy); color: #fff; border-color: var(--navy); }
.kg-tools label { display: flex; align-items: center; gap: 6px; padding: 0 6px; }
.kg-tools input[type=range] { width: 90px; }
.kg-panel { position: absolute; top: 14px; right: 14px; width: 320px; max-height: calc(100% - 28px); overflow-y: auto; }
.kg-sec { padding: 14px 16px; }
.kg-sec + .kg-sec { border-top: 1px solid var(--border); }
.kg-legend { display: flex; flex-direction: column; gap: 6px; font-size: 13px; color: var(--muted); margin-top: 6px; }
.kg-legend span { display: flex; align-items: center; gap: 6px; }
.kg-legend i { display: inline-block; width: 18px; height: 12px; border-radius: 4px; border: 1px solid #c5cdd9; }
.kg-mod { display: flex; justify-content: space-between; gap: 10px; font-size: 14px; padding: 3px 0; }
@media (max-width: 900px) {
  .kg-panel { top: auto; bottom: 10px; right: 10px; left: 10px; width: auto; max-height: 42%; }
}
.goal-card .names { font-size: 14px; margin: 6px 0; }
.cta { text-align: center; padding: 26px 20px; }
.gsi { display: flex; justify-content: center; margin: 14px 0 4px; min-height: 44px; }
.or { display: flex; align-items: center; gap: 10px; color: var(--muted); font-size: 13px; margin: 14px 0 0; }
.or::before, .or::after { content: ""; flex: 1; border-top: 1px solid var(--border); }
.avatar img { width: 100%; height: 100%; border-radius: 50%; }
@media (max-width: 600px) {
  .bar { gap: 14px; }
  nav { gap: 14px; }
  nav a { font-size: 11px; white-space: nowrap; }
  .logo { white-space: nowrap; font-size: 12px; letter-spacing: .08em; }
}