:root {
  --bg: #f6f5f1; --surface: #ffffff; --surface2: #f0eee8; --ink: #1d2230; --muted: #646b7a; --line: #e2dfd6;
  --accent: #2f5bd3; --accent-ink: #fff; --accent-soft: #e6ecfb;
  --good: #1f8a4c; --good-soft: #e3f4ea; --bad: #c4372f; --bad-soft: #fbe7e5; --warn: #a86400; --warn-soft: #fdf1dc;
  --secA: #2a8a6a; --secB: #2f5bd3; --secC: #8a46c4;
  --grid: #e8e6df; --axis: #8d93a0; --plot: #2f5bd3; --plot2: #d2662a; --shade: rgba(47, 91, 211, .18);
  --radius: 12px; --shadow: 0 1px 2px rgba(20, 24, 40, .06), 0 4px 16px rgba(20, 24, 40, .05);
  color-scheme: light;
}
@media (prefers-color-scheme: dark) { :root:not([data-theme="light"]) {
  --bg: #13161d; --surface: #1b1f29; --surface2: #232836; --ink: #e8eaf0; --muted: #9aa1b2; --line: #2d3342;
  --accent: #7c9cff; --accent-ink: #0d1020; --accent-soft: #232c4a;
  --good: #4cc282; --good-soft: #17301f; --bad: #ff7b70; --bad-soft: #3a1c1a; --warn: #f0b252; --warn-soft: #36290f;
  --secA: #4cc29a; --secB: #7c9cff; --secC: #c18cf0;
  --grid: #2a2f3c; --axis: #6f7687; --plot: #7c9cff; --plot2: #ff9b5c; --shade: rgba(124, 156, 255, .22);
  --shadow: none; color-scheme: dark;
} }
:root[data-theme="dark"] {
  --bg: #13161d; --surface: #1b1f29; --surface2: #232836; --ink: #e8eaf0; --muted: #9aa1b2; --line: #2d3342;
  --accent: #7c9cff; --accent-ink: #0d1020; --accent-soft: #232c4a;
  --good: #4cc282; --good-soft: #17301f; --bad: #ff7b70; --bad-soft: #3a1c1a; --warn: #f0b252; --warn-soft: #36290f;
  --secA: #4cc29a; --secB: #7c9cff; --secC: #c18cf0;
  --grid: #2a2f3c; --axis: #6f7687; --plot: #7c9cff; --plot2: #ff9b5c; --shade: rgba(124, 156, 255, .22);
  --shadow: none; color-scheme: dark;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
html { font-size: 16px; }
body { margin: 0; background: var(--bg); color: var(--ink); font: 16px/1.55 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif; }
a { color: var(--accent); text-decoration: none; } a:hover { text-decoration: underline; }
h1 { font-size: 1.7rem; line-height: 1.2; margin: .3em 0 .4em; letter-spacing: -.01em; }
h2 { font-size: 1.15rem; margin: 0 0 .7em; } h3 { font-size: 1.02rem; margin: 1.2em 0 .5em; }
.muted { color: var(--muted); } .small { font-size: .86rem; } .center { text-align: center; } .left { text-align: left; }
.ok { color: var(--good); font-weight: 600; } .bad-txt { color: var(--bad); } .err { color: var(--bad); } .alt-txt { color: var(--plot2); }
code { background: var(--surface2); padding: 1px 5px; border-radius: 4px; }

/* top bar */
.topbar { position: sticky; top: 0; z-index: 10; display: flex; align-items: center; gap: 18px; padding: 10px 20px; background: var(--surface); border-bottom: 1px solid var(--line); }
.brand { display: flex; align-items: center; gap: 8px; font-weight: 700; color: var(--ink); white-space: nowrap; }
.brand-mark { display: inline-grid; place-items: center; width: 44px; height: 44px; border-radius: 12px; background: var(--accent); color: var(--accent-ink); font: 700 26px/1 Georgia, serif; }
.brand-mark.sm { width: 30px; height: 30px; font-size: 18px; border-radius: 8px; }
#nav { display: flex; gap: 2px; flex-wrap: wrap; flex: 1; }
#nav a { padding: 6px 11px; border-radius: 8px; color: var(--muted); font-weight: 500; font-size: .95rem; }
#nav a:hover { background: var(--surface2); text-decoration: none; color: var(--ink); }
#nav a.active { background: var(--accent-soft); color: var(--accent); }
.top-right a { font-size: 1.2rem; color: var(--muted); margin-left: 8px; }
main { max-width: 1080px; margin: 0 auto; padding: 22px 20px 80px; }

/* cards & layout */
.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 20px 22px; margin: 0 0 18px; box-shadow: var(--shadow); }
.cols { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; } .cols > .card { margin: 0; }
.cols + .card, .cols + section { margin-top: 18px; }
.grid3 { display: grid; grid-template-columns: repeat(3, 1fr); gap: 14px; margin-bottom: 18px; }
.stat { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 14px 18px; }
.stat-n { font-size: 1.8rem; font-weight: 700; font-variant-numeric: tabular-nums; } .stat-n small { font-size: .9rem; color: var(--muted); font-weight: 500; }
.hero { display: flex; justify-content: space-between; align-items: center; gap: 20px; margin-bottom: 18px; }
.count { text-align: center; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 10px 22px; }
.big-num { font-size: 2.6rem; font-weight: 800; color: var(--accent); line-height: 1.1; font-variant-numeric: tabular-nums; }
.back { display: inline-block; margin-bottom: 4px; font-size: .92rem; }
.center-card { max-width: 620px; margin: 30px auto; text-align: center; }
.facts { padding-left: 1.1em; margin: 0 0 .6em; } .facts li { margin: .35em 0; }
.warn { background: var(--warn-soft); color: var(--warn); padding: 10px 14px; border-radius: 8px; }

/* buttons */
.btn { display: inline-flex; align-items: center; gap: 6px; border: 1px solid var(--line); background: var(--surface); color: var(--ink); padding: 9px 16px; border-radius: 9px; font: inherit; font-weight: 600; cursor: pointer; text-decoration: none !important; }
.btn:hover { border-color: var(--accent); }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); }
.btn.primary:hover { filter: brightness(1.08); }
.btn.ghost { background: transparent; }
.btn.danger { color: var(--bad); border-color: var(--bad); }
.btn.danger-solid { background: var(--bad); border-color: var(--bad); color: #fff; }
.btn.danger-solid:disabled { opacity: .4; }
.danger-zone { border: 1.5px solid var(--bad); }
.danger-zone h2 { color: var(--bad); }
.warnbox { background: var(--bad-soft); color: var(--bad); padding: 10px 14px; border-radius: 8px; margin: 12px 0 14px; }
.rform { margin-top: 12px; }
.btn.small { padding: 5px 11px; font-size: .88rem; }
.btn:disabled { opacity: .45; cursor: default; }
.btns { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 12px; } .btns.center { justify-content: center; }

/* tags, chips, levels */
.tag { display: inline-block; font-size: .72rem; font-weight: 700; padding: 1px 7px; border-radius: 99px; color: #fff; vertical-align: 2px; }
.tag.secA { background: var(--secA); } .tag.secB { background: var(--secB); } .tag.secC { background: var(--secC); }
.chip { display: inline-flex; align-items: center; gap: 6px; padding: 4px 10px; border-radius: 99px; background: var(--surface2); border: 1px solid var(--line); color: var(--ink); font-size: .86rem; margin: 2px; position: relative; overflow: hidden; }
.chip i { position: absolute; left: 0; bottom: 0; height: 3px; width: var(--p); background: var(--good); }
.chip.secA { border-left: 4px solid var(--secA); } .chip.secB { border-left: 4px solid var(--secB); } .chip.secC { border-left: 4px solid var(--secC); }
.chip.mock { background: var(--accent-soft); color: var(--accent); font-weight: 600; } .chip.ghost { background: transparent; color: var(--muted); }
.lvl { font-size: .7rem; font-weight: 700; padding: 1px 7px; border-radius: 99px; white-space: nowrap; }
.lvl0 { background: var(--surface2); color: var(--muted); } .lvl1 { background: var(--bad-soft); color: var(--bad); } .lvl2 { background: var(--warn-soft); color: var(--warn); } .lvl3 { background: var(--good-soft); color: var(--good); }
.bar { height: 8px; background: var(--surface2); border-radius: 99px; overflow: hidden; margin-top: 8px; } .bar i { display: block; height: 100%; background: var(--good); }
.bar.thin { height: 4px; margin: 6px 0 14px; } .bar.thin i { background: var(--accent); }

/* home */
.todos { display: grid; gap: 8px; }
.todo { display: block; padding: 11px 14px; border: 1px solid var(--line); border-radius: 10px; background: var(--surface2); color: var(--ink); }
.todo:hover { border-color: var(--accent); text-decoration: none; } .todo b { display: block; } .todo span { color: var(--muted); font-size: .88rem; }
.plan { display: grid; gap: 4px; }
.week { display: grid; grid-template-columns: 90px 1fr; gap: 10px; align-items: center; padding: 6px 8px; border-radius: 8px; }
.week.now { background: var(--accent-soft); } .week.past { opacity: .6; }
.wk-d { font-size: .82rem; font-weight: 600; } .wk-d span { color: var(--muted); font-weight: 400; }

/* learn */
.units { display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 14px; }
.unit-card { display: block; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px; color: var(--ink); }
.unit-card:hover { border-color: var(--accent); text-decoration: none; } .unit-card h3 { margin: .5em 0 .3em; }
.u-top { display: flex; justify-content: space-between; align-items: center; }
.lesson-list li { margin: .4em 0; }
.lesson { font-size: 1.02rem; } .lesson h1 { margin-top: .2em; }
.lesson ul, .lesson ol { padding-left: 1.3em; } .lesson li { margin: .3em 0; }
.callout { background: var(--warn-soft); border-left: 4px solid var(--warn); padding: 10px 14px; border-radius: 6px; margin: 1em 0; }
.callout ul { margin: .3em 0 0; }
.tip { background: var(--accent-soft); border-radius: 8px; padding: 9px 13px; }
.tip::before { content: "💡 "; }
.steps { border-left: 3px solid var(--accent); padding: 4px 0 4px 14px; margin: .8em 0; } .steps p { margin: .35em 0; }
.big { font-size: 1.25rem; }
.tbl { border-collapse: collapse; width: 100%; margin: .6em 0; } .tbl th, .tbl td { text-align: left; padding: 7px 10px; border-bottom: 1px solid var(--line); vertical-align: middle; }
.tbl th { font-size: .82rem; color: var(--muted); font-weight: 600; }
.tbl.skills td:nth-child(2) { width: 110px; }

/* practice */
.practice-head h1 { margin-bottom: .1em; }
.ph-meta { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.switch { margin-left: auto; font-size: .88rem; color: var(--muted); display: flex; gap: 6px; align-items: center; cursor: pointer; }
.skill-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(230px, 1fr)); gap: 8px; }
.skill { display: grid; grid-template-columns: 1fr auto; gap: 2px 8px; padding: 10px 12px; border: 1px solid var(--line); border-radius: 10px; color: var(--ink); background: var(--surface2); }
.skill:hover { border-color: var(--accent); text-decoration: none; } .skill small { grid-column: 1 / -1; color: var(--muted); }
.qcard .q { font-size: 1.12rem; margin: 6px 0 16px; }
.q .center { margin-top: 10px; }
.choices { display: grid; gap: 8px; }
.choice { display: flex; align-items: center; gap: 12px; padding: 10px 14px; border: 1.5px solid var(--line); border-radius: 10px; cursor: pointer; background: var(--surface); }
.choice:hover { border-color: var(--accent); } .choice input { position: absolute; opacity: 0; pointer-events: none; }
.choice .letter { flex: none; width: 28px; height: 28px; border-radius: 50%; display: grid; place-items: center; background: var(--surface2); font-weight: 700; font-size: .9rem; }
.choice.sel { border-color: var(--accent); background: var(--accent-soft); } .choice.sel .letter { background: var(--accent); color: var(--accent-ink); }
.choice.right { border-color: var(--good); background: var(--good-soft); } .choice.right .letter { background: var(--good); color: #fff; }
.choice.wrong { border-color: var(--bad); background: var(--bad-soft); } .choice.wrong .letter { background: var(--bad); color: #fff; }
.choices:has(svg.graph) { grid-template-columns: repeat(auto-fill, minmax(210px, 1fr)); }
.choices:has(svg.graph) .choice { flex-direction: column; align-items: flex-start; }
.choice.dim { opacity: .55; } .choices.static .choice { cursor: default; }
.choice .ctext { overflow-x: auto; }
.typein input { width: 100%; max-width: 420px; font: inherit; font-size: 1.15rem; padding: 10px 12px; border: 1.5px solid var(--line); border-radius: 9px; background: var(--surface); color: var(--ink); }
.typein input:focus, .form input:focus, select:focus { outline: 2px solid var(--accent); border-color: transparent; }
.hint { margin-top: 14px; padding: 10px 14px; background: var(--warn-soft); border-radius: 8px; }
.fb { margin-top: 16px; padding: 10px 14px; border-radius: 8px; font-weight: 600; }
.fb.good { background: var(--good-soft); color: var(--good); } .fb.bad { background: var(--bad-soft); color: var(--bad); }
.sol { margin-top: 12px; }
.tutor { margin-top: 16px; border-top: 1px solid var(--line); padding-top: 12px; }
.tmsg { padding: 10px 14px; border-radius: 10px; margin: 0 0 8px; max-width: 90%; }
.tmsg p { margin: .3em 0; }
.tmsg.bot { background: var(--accent-soft); } .tmsg.me { background: var(--surface2); margin-left: auto; width: fit-content; }
.tmsg.pending { color: var(--muted); font-style: italic; } .tmsg.err { background: var(--bad-soft); color: var(--bad); }
.tform { display: flex; gap: 8px; } .tform input { flex: 1; font: inherit; padding: 8px 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); color: var(--ink); }

/* graphs */
svg.graph { background: var(--surface); border-radius: 6px; max-width: 100%; height: auto; }
.g-grid { stroke: var(--grid); stroke-width: 1; } .g-axis { stroke: var(--axis); stroke-width: 1.4; } .g-axis-head { fill: var(--axis); }
.g-lab { fill: var(--muted); font-size: 9px; font-family: system-ui, sans-serif; }
.g-line { stroke: var(--plot); stroke-width: 2.4; fill: none; } .g-line.dash { stroke-dasharray: 7 5; } .g-line.alt { stroke: var(--plot2); }
.g-shade { fill: var(--shade); } .g-pt { fill: var(--plot); } .g-ptlab { fill: var(--ink); font-size: 10px; }
.g-poly { fill: var(--shade); stroke: var(--plot); stroke-width: 2; }
svg.nline { max-width: 100%; height: auto; vertical-align: middle; }
.nl-ray { stroke: var(--plot); stroke-width: 4; } .nl-head { fill: var(--plot); }
.nl-closed { fill: var(--plot); stroke: var(--plot); stroke-width: 2; } .nl-open { fill: var(--surface); stroke: var(--plot); stroke-width: 2.4; }
.chart .target { stroke: var(--good); stroke-dasharray: 5 4; } .chart .target-lab { fill: var(--good); }
.chart .g-line { stroke-width: 2.5; }

/* tests */
.test-row { display: flex; justify-content: space-between; align-items: center; gap: 12px; padding: 10px 0; border-bottom: 1px solid var(--line); }
.test-head { position: sticky; top: 55px; z-index: 5; display: flex; justify-content: space-between; align-items: center; gap: 12px; background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 10px 16px; margin-bottom: 14px; }
.timer { font-variant-numeric: tabular-nums; font-weight: 700; } .timer.low { color: var(--bad); }
.test-body { display: grid; grid-template-columns: 170px 1fr; gap: 16px; align-items: start; }
.qnav { display: grid; grid-template-columns: repeat(5, 1fr); gap: 5px; position: sticky; top: 120px; }
.qn { border: 1px solid var(--line); background: var(--surface); color: var(--ink); border-radius: 6px; padding: 6px 0; font: inherit; font-size: .82rem; cursor: pointer; }
.qn.done { background: var(--accent-soft); border-color: var(--accent); } .qn.cur { outline: 2px solid var(--accent); font-weight: 700; } .qn.flag { box-shadow: inset 0 -3px 0 var(--warn); }
details.rev { padding: 12px 18px; } details.rev summary { cursor: pointer; }
details.rev.right { border-left: 4px solid var(--good); } details.rev.wrong { border-left: 4px solid var(--bad); } details.rev.blank { border-left: 4px solid var(--line); }

/* review / progress */
.mistake { padding: 12px 0; border-bottom: 1px solid var(--line); } .mistake .q { margin: 4px 0; }
.heat { display: grid; grid-template-rows: repeat(7, 14px); grid-auto-flow: column; grid-auto-columns: 14px; gap: 3px; }
.hm { border-radius: 3px; background: var(--surface2); } .hm.h1 { background: color-mix(in srgb, var(--good) 35%, transparent); } .hm.h2 { background: color-mix(in srgb, var(--good) 65%, transparent); } .hm.h3 { background: var(--good); }

/* forms & worksheets */
.form label, .ws-opts label { display: block; margin: 0 0 12px; font-weight: 600; font-size: .92rem; }
.form input, .ws-opts input, select { display: block; margin-top: 4px; font: inherit; padding: 8px 10px; border: 1px solid var(--line); border-radius: 8px; background: var(--surface); color: var(--ink); max-width: 340px; width: 100%; }
fieldset { border: 1px solid var(--line); border-radius: 10px; margin: 0 0 12px; padding: 8px 14px 10px; } legend { font-weight: 700; padding: 0 6px; }
label.cb { display: inline-flex !important; align-items: center; gap: 6px; margin: 4px 16px 4px 0 !important; font-weight: 400 !important; }
label.cb input { width: auto; display: inline; margin: 0; }
.ws-opts { display: flex; gap: 20px; flex-wrap: wrap; align-items: end; margin-top: 10px; }
.sheet { background: #fff; color: #111; padding: 28px 34px; border-radius: 8px; margin: 14px 0; }
.sheet .muted { color: #555; }
.sheet-h { display: flex; justify-content: space-between; border-bottom: 2px solid #111; padding-bottom: 6px; margin-bottom: 8px; }
ol.ws > li { margin: 0 0 18px; break-inside: avoid; } .wsc { display: flex; flex-wrap: wrap; gap: 6px 26px; margin-top: 4px; }
.work { height: 90px; } .key { columns: 4; } .sols li { margin: 4px 0; font-size: .9rem; }
.sheet svg.graph { background: #fff; }

/* login */
.login-body { display: grid; place-items: center; min-height: 100vh; padding: 16px; }
.login-card { width: 100%; max-width: 360px; background: var(--surface); border: 1px solid var(--line); border-radius: 16px; padding: 30px 28px; box-shadow: var(--shadow); text-align: center; }
.login-card h1 { margin: 14px 0 2px; } .login-card label { display: block; text-align: left; font-weight: 600; margin: 20px 0 6px; font-size: .9rem; }
.login-card input { width: 100%; font: inherit; padding: 10px 12px; border: 1px solid var(--line); border-radius: 9px; background: var(--surface); color: var(--ink); }
.login-card .btn { width: 100%; justify-content: center; margin-top: 16px; }

@media (max-width: 760px) {
  .topbar { flex-wrap: wrap; gap: 8px; padding: 8px 16px; } #nav { order: 3; flex-basis: 100%; overflow-x: auto; flex-wrap: nowrap; }
  main { padding: 16px 16px 60px; } .cols, .grid3 { grid-template-columns: 1fr; } .hero { flex-direction: column; align-items: stretch; }
  .test-body { grid-template-columns: 1fr; } .qnav { position: static; grid-template-columns: repeat(8, 1fr); } .test-head { top: 92px; }
  .key { columns: 2; } .week { grid-template-columns: 70px 1fr; }
}
@media print {
  .topbar, .noprint { display: none !important; } body, main { background: #fff; padding: 0; margin: 0; max-width: none; }
  .sheet { padding: 0; margin: 0; } .sheet.pb { break-before: page; }
}