:root {
  --bg: #f6f5f1; --surface: #ffffff; --surface-2: #f0eee8; --ink: #1d1f24; --ink-2: #555a64; --ink-3: #8a8f99;
  --line: #e2dfd6; --accent: #2b59c3; --accent-ink: #ffffff; --accent-soft: #e6ecfa;
  --ok: #1f8a4c; --ok-soft: #e3f4ea; --bad: #c0392b; --bad-soft: #fbe9e7; --warn: #b7791f; --warn-soft: #fbf1df;
  --gold: #c9a227; --silver: #9aa3ad; --bronze: #b0743b;
  --s0: #7a8ca6; --s1: #3f8f7a; --s2: #2b59c3; --s3: #7a4bc2; --s4: #c2410c;
  --radius: 10px; --shadow: 0 1px 2px rgba(0,0,0,.05), 0 2px 8px rgba(0,0,0,.04);
  --font: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --serif: "Iowan Old Style", "Palatino Linotype", Palatino, Georgia, "Times New Roman", serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #15171b; --surface: #1d2025; --surface-2: #252931; --ink: #e8e9ec; --ink-2: #b2b7c0; --ink-3: #7f8590;
    --line: #2f343d; --accent: #7aa2ff; --accent-ink: #0d1424; --accent-soft: #23304d;
    --ok: #4cc27f; --ok-soft: #1c3528; --bad: #ff7a6b; --bad-soft: #3d2220; --warn: #e3b05a; --warn-soft: #3a2f1b;
    --s0: #9aabc2; --s1: #5cc0a4; --s2: #7aa2ff; --s3: #b18cf0; --s4: #f08a54;
    --shadow: none; color-scheme: dark;
  }
  .page-img, .fig img { filter: invert(.88) hue-rotate(180deg); }
}
* { box-sizing: border-box; }
html, body { margin: 0; background: var(--bg); color: var(--ink); font: 15px/1.55 var(--font); }
a { color: var(--accent); text-decoration: none; } a:hover { text-decoration: underline; }
h1, h2, h3 { line-height: 1.25; margin: 0 0 .6em; } h1 { font-size: 1.6rem; } h2 { font-size: 1.2rem; } h3 { font-size: 1.02rem; }
button, input, select, textarea { font: inherit; color: inherit; }
.wrap { max-width: 1120px; margin: 0 auto; padding: 0 16px; }
header.top { background: var(--surface); border-bottom: 1px solid var(--line); position: sticky; top: 0; z-index: 10; }
header.top .wrap { display: flex; align-items: center; gap: 18px; height: 56px; }
.brand { font-weight: 700; letter-spacing: .2px; color: var(--ink); font-size: 1.08rem; white-space: nowrap; }
.brand b { color: var(--accent); }
nav.main { display: flex; gap: 4px; flex: 1; overflow-x: auto; scrollbar-width: none; }
nav.main a { padding: 7px 11px; border-radius: 8px; color: var(--ink-2); white-space: nowrap; }
nav.main a.on { background: var(--accent-soft); color: var(--accent); font-weight: 600; text-decoration: none; }
nav.main a:hover { text-decoration: none; background: var(--surface-2); }
.top-right { display: flex; align-items: center; gap: 8px; }
.lang-toggle { display: inline-flex; border: 1px solid var(--line); border-radius: 8px; overflow: hidden; }
.lang-toggle button { border: 0; background: transparent; padding: 4px 9px; cursor: pointer; color: var(--ink-3); font-size: .85rem; }
.lang-toggle button.on { background: var(--ink); color: var(--bg); }
main { padding: 22px 0 60px; }
.grid { display: grid; gap: 16px; }
.g2 { grid-template-columns: 1fr 1fr; } .g3 { grid-template-columns: repeat(3, 1fr); } .g-side { grid-template-columns: minmax(0, 1fr) 340px; }
@media (max-width: 900px) { .g2, .g3, .g-side { grid-template-columns: 1fr; } }
.card { background: var(--surface); border: 1px solid var(--line); border-radius: var(--radius); padding: 16px 18px; box-shadow: var(--shadow); min-width: 0; }
.card h2, .card h3 { margin-top: 0; }
.muted { color: var(--ink-3); } .small { font-size: .86rem; } .tiny { font-size: .78rem; }
.row { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; } .row.between { justify-content: space-between; }
.stack > * + * { margin-top: 10px; }
.btn { display: inline-flex; align-items: center; justify-content: center; gap: 6px; border: 1px solid var(--line); background: var(--surface);
  padding: 8px 14px; border-radius: 8px; cursor: pointer; color: var(--ink); white-space: nowrap; }
.btn:hover { background: var(--surface-2); text-decoration: none; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--accent-ink); font-weight: 600; }
.btn.primary:hover { filter: brightness(1.06); }
.btn.ghost { background: transparent; border-color: transparent; color: var(--ink-2); }
.btn.danger { color: var(--bad); }
.btn.sm { padding: 4px 10px; font-size: .86rem; }
.btn:disabled { opacity: .5; cursor: default; }
input[type=text], input[type=email], input[type=password], input[type=number], input[type=datetime-local], select, textarea {
  width: 100%; border: 1px solid var(--line); background: var(--surface); border-radius: 8px; padding: 8px 10px; outline: none; }
input:focus, select:focus, textarea:focus { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
textarea { min-height: 120px; resize: vertical; font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; font-size: .88rem; }
label.f { display: block; } label.f > span { display: block; font-size: .85rem; color: var(--ink-2); margin-bottom: 4px; }
label.chk { display: flex; gap: 8px; align-items: flex-start; font-size: .9rem; color: var(--ink-2); }
label.chk input { margin-top: 4px; }
.pill { display: inline-flex; align-items: center; gap: 4px; border-radius: 999px; padding: 1px 9px; font-size: .78rem; background: var(--surface-2); color: var(--ink-2); white-space: nowrap; }
.pill.st0 { background: color-mix(in srgb, var(--s0) 16%, transparent); color: var(--s0); }
.pill.st1 { background: color-mix(in srgb, var(--s1) 16%, transparent); color: var(--s1); }
.pill.st2 { background: color-mix(in srgb, var(--s2) 16%, transparent); color: var(--s2); }
.pill.st3 { background: color-mix(in srgb, var(--s3) 16%, transparent); color: var(--s3); }
.pill.st4 { background: color-mix(in srgb, var(--s4) 16%, transparent); color: var(--s4); }
.pill.ok { background: var(--ok-soft); color: var(--ok); } .pill.bad { background: var(--bad-soft); color: var(--bad); } .pill.warn { background: var(--warn-soft); color: var(--warn); }
.notice { border-radius: 8px; padding: 10px 12px; background: var(--accent-soft); color: var(--ink); font-size: .9rem; }
.notice.warn { background: var(--warn-soft); } .notice.ok { background: var(--ok-soft); } .notice.bad { background: var(--bad-soft); }
.err { color: var(--bad); font-size: .9rem; }
/* auth */
.auth { max-width: 460px; margin: 6vh auto; }
.auth .brand { font-size: 1.6rem; display: block; margin-bottom: 4px; }
/* ladder */
.ladder { display: grid; grid-template-columns: repeat(5, 1fr); gap: 6px; margin: 10px 0 4px; }
.ladder .step { border-radius: 8px; padding: 8px 9px; background: var(--surface-2); color: var(--ink-3); font-size: .78rem; line-height: 1.3; min-height: 54px; position: relative; overflow: hidden; }
.ladder .step b { display: block; font-size: .82rem; color: var(--ink-2); }
.ladder .step.done { background: color-mix(in srgb, var(--accent) 14%, var(--surface)); }
.ladder .step.cur { outline: 2px solid var(--accent); background: var(--accent-soft); }
.ladder .step.cur b { color: var(--accent); }
.ladder .bar { position: absolute; left: 0; bottom: 0; height: 4px; background: var(--accent); }
@media (max-width: 600px) { .ladder { grid-template-columns: repeat(5, minmax(0,1fr)); } .ladder .step { font-size: .68rem; padding: 6px; } .ladder .step span { display: none; } }
.big-num { font-size: 2.3rem; font-weight: 700; letter-spacing: -.5px; line-height: 1; font-variant-numeric: tabular-nums; }
.bars .b { display: grid; grid-template-columns: 150px 1fr 48px; gap: 8px; align-items: center; font-size: .86rem; margin: 5px 0; }
.bars .track { height: 8px; border-radius: 99px; background: var(--surface-2); position: relative; }
.bars .fill { position: absolute; left: 0; top: 0; bottom: 0; border-radius: 99px; background: var(--accent); }
.bars .unc { position: absolute; top: -2px; bottom: -2px; border-radius: 99px; background: color-mix(in srgb, var(--accent) 22%, transparent); }
/* problem list */
.plist { display: grid; gap: 8px; }
.pcard { display: grid; grid-template-columns: 1fr auto; gap: 6px 14px; align-items: center; padding: 11px 14px; border: 1px solid var(--line);
  background: var(--surface); border-radius: var(--radius); color: var(--ink); }
.pcard:hover { border-color: var(--accent); text-decoration: none; }
.pcard .t { font-weight: 600; } .pcard .meta { display: flex; gap: 6px; flex-wrap: wrap; align-items: center; }
.pcard .rt { text-align: right; font-variant-numeric: tabular-nums; color: var(--ink-2); font-size: .9rem; }
.mark { width: 10px; height: 10px; border-radius: 99px; display: inline-block; background: var(--line); }
.mark.solved { background: var(--ok); } .mark.tried { background: var(--warn); }
.filters { display: grid; grid-template-columns: 2fr repeat(5, 1fr); gap: 8px; margin-bottom: 12px; }
@media (max-width: 900px) { .filters { grid-template-columns: 1fr 1fr; } }
/* problem page */
.statement { font-family: var(--serif); font-size: 1.08rem; line-height: 1.65; }
.statement p { margin: 0 0 .8em; }
.md img, .fig img { max-width: 100%; height: auto; display: block; margin: 10px auto; background: #fff; border-radius: 6px; }
.md figure { margin: 0; }
.md table { border-collapse: collapse; } .md td, .md th { border: 1px solid var(--line); padding: 4px 8px; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: 2px 0; }
.part { border: 1px solid var(--line); border-radius: 8px; padding: 10px 12px; background: var(--surface); }
.part.ok { border-color: var(--ok); background: var(--ok-soft); }
.part .inp { display: grid; grid-template-columns: auto 1fr auto auto; gap: 8px; align-items: center; }
.part .lab { font-weight: 600; font-family: var(--serif); }
.part code { font-size: .85rem; }
.hint { border-left: 3px solid var(--warn); background: var(--warn-soft); padding: 8px 12px; border-radius: 0 8px 8px 0; }
.chat { display: flex; flex-direction: column; gap: 8px; max-height: 360px; overflow-y: auto; padding: 4px; }
.msg { padding: 8px 11px; border-radius: 10px; max-width: 92%; }
.msg.user { align-self: flex-end; background: var(--accent-soft); } .msg.assistant { align-self: flex-start; background: var(--surface-2); }
.thumbs { display: flex; gap: 8px; flex-wrap: wrap; }
.thumbs img { width: 84px; height: 108px; object-fit: cover; border-radius: 6px; border: 1px solid var(--line); background: #fff; }
.page-img { width: 100%; border: 1px solid var(--line); border-radius: 6px; background: #fff; }
.scheme td { padding: 4px 6px; vertical-align: top; border-bottom: 1px solid var(--line); }
table.t { width: 100%; border-collapse: collapse; font-size: .9rem; }
table.t th, table.t td { text-align: left; padding: 7px 8px; border-bottom: 1px solid var(--line); }
table.t th { color: var(--ink-3); font-weight: 600; font-size: .8rem; text-transform: uppercase; letter-spacing: .3px; }
table.t tr.me td { background: var(--accent-soft); }
.num { text-align: right !important; font-variant-numeric: tabular-nums; }
.tabs { display: flex; gap: 4px; border-bottom: 1px solid var(--line); margin-bottom: 14px; overflow-x: auto; }
.tabs a { padding: 8px 12px; color: var(--ink-2); border-bottom: 2px solid transparent; white-space: nowrap; }
.tabs a.on { color: var(--accent); border-bottom-color: var(--accent); font-weight: 600; text-decoration: none; }
.score-ring { font-size: 2rem; font-weight: 700; }
.modal-bg { position: fixed; inset: 0; background: rgba(0,0,0,.35); display: grid; place-items: center; z-index: 50; padding: 16px; }
.modal { background: var(--surface); border-radius: 12px; padding: 18px; max-width: 440px; width: 100%; box-shadow: 0 10px 40px rgba(0,0,0,.25); }
.toast { position: fixed; bottom: 18px; left: 50%; transform: translateX(-50%); background: var(--ink); color: var(--bg); padding: 9px 16px; border-radius: 8px; z-index: 60; font-size: .9rem; }
.badge { display: inline-flex; align-items: center; gap: 6px; padding: 4px 10px; border-radius: 999px; border: 1px solid var(--line); font-size: .82rem; }
.badge i { width: 10px; height: 10px; border-radius: 99px; display: inline-block; background: var(--line); }
.badge.gold i { background: var(--gold); } .badge.silver i { background: var(--silver); } .badge.bronze i { background: var(--bronze); }
.cmp { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; }
@media (max-width: 800px) { .cmp { grid-template-columns: 1fr; } }
.spark { width: 100%; height: 64px; }
.spinner { width: 14px; height: 14px; border: 2px solid var(--line); border-top-color: var(--accent); border-radius: 99px; display: inline-block; animation: spin .8s linear infinite; }
@keyframes spin { to { transform: rotate(360deg); } }
.foot { color: var(--ink-3); font-size: .8rem; text-align: center; padding: 20px 0 30px; }
.kv { display: grid; grid-template-columns: auto 1fr; gap: 4px 12px; font-size: .9rem; }
.kv dt { color: var(--ink-3); } .kv dd { margin: 0; }
details > summary { cursor: pointer; color: var(--ink-2); }
/* mobile header: nav on its own scrollable row */
@media (max-width: 760px) {
  header.top .wrap { flex-wrap: wrap; height: auto; padding-top: 8px; padding-bottom: 6px; gap: 6px 10px; }
  .brand { flex: 1; }
  nav.main { order: 3; flex-basis: 100%; }
  .top-right .user-name { display: none; }
}
.info-src { font-size: .88rem; margin-bottom: 10px; padding-bottom: 10px; border-bottom: 1px solid var(--line); }
.hint { display: flex; gap: 6px; } .hint .md p { margin: 0; } .hint .md p + p { margin-top: 6px; }
.md > p:first-child { margin-top: 0; } .md > p:last-child { margin-bottom: 0; }
@media (max-width: 600px) {
  .ladder .step b { font-size: .64rem; overflow-wrap: anywhere; font-weight: 600; }
  .pcard { grid-template-columns: 1fr; }
  .pcard .rt { text-align: left; display: flex; gap: 10px; align-items: baseline; flex-wrap: wrap; }
  .part .inp { grid-template-columns: auto 1fr; }
  .part .inp > span:nth-child(3), .part .inp > span:nth-child(4) { grid-column: 2; }
  .big-num { font-size: 1.9rem; }
}

/* ===================== v0.2 (Gradient) ===================== */
:root { --m-mastered: #1f8a4c; --m-proficient: #7cc69a; --m-learning: #e0a43a; --m-none: #d5d2c8; --olymp: #7a4bc2; }
@media (prefers-color-scheme: dark) { :root { --m-mastered: #4cc27f; --m-proficient: #2f7a52; --m-learning: #c9902f; --m-none: #3a3f48; --olymp: #b18cf0; } }
.brand { display: inline-flex; align-items: center; gap: 8px; }
.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 9px; overflow: hidden; background: var(--surface); }
.seg button { border: 0; background: transparent; padding: 5px 10px; cursor: pointer; color: var(--ink-2); display: inline-flex; gap: 5px; align-items: center; font-size: .88rem; }
.seg button.on { background: var(--accent); color: var(--accent-ink); font-weight: 600; }
.seg.sm button { padding: 4px 9px; }
.seg-ico { font-weight: 700; }
@media (max-width: 1100px) { .seg.sm .seg-lab { display: none; } }
.mdot { width: 10px; height: 10px; border-radius: 99px; display: inline-block; background: var(--m-none); flex: none; vertical-align: middle; }
.mdot.m-mastered { background: var(--m-mastered); } .mdot.m-proficient { background: var(--m-proficient); }
.mdot.m-learning { background: var(--m-learning); } .mdot.m-inferred { background: transparent; border: 2px dashed var(--m-mastered); width: 11px; height: 11px; }
.mbar { display: flex; height: 12px; border-radius: 99px; overflow: hidden; background: var(--m-none); }
.mbar span { display: block; height: 100%; } .mbar .m-mastered { background: var(--m-mastered); } .mbar .m-proficient { background: var(--m-proficient); }
.mbar .m-learning { background: var(--m-learning); } .mbar .m-inferred { background: repeating-linear-gradient(45deg, var(--m-proficient) 0 4px, transparent 4px 8px); } .mbar .m-none { background: var(--m-none); }
.pill.school { background: color-mix(in srgb, var(--s1) 16%, transparent); color: var(--s1); }
.onboard { border-color: var(--accent); background: linear-gradient(135deg, var(--accent-soft), var(--surface) 70%); }
.legend { gap: 14px; color: var(--ink-2); }
/* knowledge graph */
.gwrap { position: relative; }
.gctl { position: absolute; right: 10px; top: 10px; z-index: 2; display: flex; gap: 4px; }
.gmap { width: 100%; height: 68vh; min-height: 420px; display: block; cursor: grab; touch-action: none; user-select: none; background: var(--surface); }
.gmap:active { cursor: grabbing; }
.gband { fill: var(--surface); } .gband.alt { fill: var(--surface-2); }
.gband-label { fill: var(--ink-3); font-size: 12px; font-weight: 600; text-transform: uppercase; letter-spacing: .4px; }
.gcol { fill: var(--ink-2); font-size: 13px; font-weight: 700; } .gcol.me { fill: var(--accent); }
.gcol-hl { fill: var(--accent-soft); opacity: .35; }
.gedge { fill: none; stroke: var(--ink-3); stroke-width: 1.1; opacity: .16; } .gedge.hot { stroke: var(--accent); stroke-width: 2; opacity: 1; } .gedge.dim { opacity: .08; }
.gnode { cursor: pointer; } .gnode rect { fill: var(--surface); stroke: var(--line); stroke-width: 1.4; }
.gnode .glabel { font-size: 12px; fill: var(--ink); } .gnode .gdot { fill: var(--m-none); } .gnode .gstar { fill: var(--olymp); font-size: 12px; }
.gnode.olymp rect { stroke: var(--olymp); stroke-dasharray: 0; }
.gnode.m-learning rect { fill: color-mix(in srgb, var(--m-learning) 18%, var(--surface)); } .gnode.m-learning .gdot { fill: var(--m-learning); }
.gnode.m-proficient rect { fill: color-mix(in srgb, var(--m-proficient) 30%, var(--surface)); } .gnode.m-proficient .gdot { fill: var(--m-proficient); }
.gnode.m-mastered rect { fill: color-mix(in srgb, var(--m-mastered) 30%, var(--surface)); stroke: var(--m-mastered); } .gnode.m-mastered .gdot { fill: var(--m-mastered); }
.gnode.m-inferred rect { stroke: var(--m-mastered); stroke-dasharray: 4 3; } .gnode.m-inferred .gdot { fill: var(--m-proficient); }
.gnode.sel rect { stroke: var(--accent); stroke-width: 3; } .gnode.dim { opacity: .3; } .gnode:hover rect { stroke: var(--accent); }
.npanel h2 { font-size: 1.15rem; }
.nlist { display: grid; grid-template-columns: repeat(auto-fill, minmax(280px, 1fr)); gap: 6px; }
.nitem { display: flex; align-items: center; gap: 8px; padding: 6px 8px; border-radius: 8px; color: var(--ink); }
.nitem:hover { background: var(--surface-2); text-decoration: none; } .nitem .tiny { margin-left: auto; text-align: right; }
.chips { display: flex; flex-wrap: wrap; gap: 6px; }
.nchip { display: inline-flex; align-items: center; gap: 6px; border: 1px solid var(--line); border-radius: 99px; padding: 3px 10px; font-size: .85rem; color: var(--ink); background: var(--surface); }
.nchip:hover { border-color: var(--accent); text-decoration: none; }
/* lessons */
.lesson h1 { margin-top: 8px; } .lesson-body { font-size: 1.02rem; line-height: 1.7; } .lesson-body h3 { margin-top: 1.2em; }
.formulas { background: var(--surface-2); border-radius: 10px; padding: 8px 14px; margin: 14px 0; }
.example { border-left: 3px solid var(--accent); padding: 8px 14px; margin: 14px 0; background: var(--accent-soft); border-radius: 0 10px 10px 0; }
.ex-sol { margin-top: 8px; padding-top: 8px; border-top: 1px dashed var(--line); }
/* choices & quizzes */
.choices { display: grid; gap: 6px; }
.choice { display: flex; gap: 10px; align-items: flex-start; text-align: left; border: 1px solid var(--line); background: var(--surface); border-radius: 10px; padding: 8px 12px; cursor: pointer; color: var(--ink); font: inherit; }
.choice:hover:not(:disabled) { border-color: var(--accent); } .choice:disabled { cursor: default; }
.choice .md p { margin: 0; } .choice .cmark { font-weight: 700; color: var(--ink-3); min-width: 1.2em; }
.choice.chosen { border-color: var(--accent); background: var(--accent-soft); } .choice.chosen .cmark { color: var(--accent); }
.choice.right { border-color: var(--ok); background: var(--ok-soft); } .choice.wrong { border-color: var(--bad); background: var(--bad-soft); }
.part.missed { border-color: var(--bad); }
.qitem.ok { border-left: 4px solid var(--ok); } .qitem.miss { border-left: 4px solid var(--bad); }
.qpart { margin-top: 10px; } .qpart .inp { display: grid; grid-template-columns: auto 1fr auto; gap: 8px; align-items: center; }
.sticky-head { position: sticky; top: 62px; z-index: 5; }
@media (max-width: 760px) { .sticky-head { top: 96px; } }
.tgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(130px, 1fr)); gap: 10px; }
.tcard { border: 1px solid var(--line); border-radius: 10px; padding: 10px; display: flex; flex-direction: column; gap: 6px; align-items: flex-start; }
/* social */
.friend-code { font: 700 1.6rem/1.2 ui-monospace, SFMono-Regular, Menlo, Consolas, monospace; letter-spacing: 3px; color: var(--accent); }
.feed-row { padding: 4px 0; border-bottom: 1px solid var(--line); } .feed-row:last-child { border-bottom: 0; }
a.notice { display: block; color: var(--ink); } a.notice:hover { text-decoration: none; filter: brightness(.98); }
@media (max-width: 760px) { header.top .wrap { gap: 6px 8px; } .top-right { gap: 6px; } }

header.top .wrap { max-width: 1320px; }
nav.main a { padding: 7px 9px; }
@media (max-width: 1500px) { .seg.sm .seg-lab { display: none; } .seg.sm button { padding: 4px 10px; font-size: 1rem; } }
@media (max-width: 1250px) { nav.main a { padding: 6px 7px; font-size: .92rem; } }
.gmap { height: 70vh; }
@media (max-width: 760px) { .gmap { height: 62vh; min-height: 360px; } }

/* ===================== v0.3: knowledge map (lanes), English, vocabulary ===================== */
:root { --a0: #2b59c3; --a1: #0f8b8d; --a2: #c2410c; --a3: #7a4bc2; --a4: #b7791f; --a5: #1f8a4c; --a6: #c0392b; --a7: #4f6d8f; --hdr: 56px; }
@media (prefers-color-scheme: dark) { :root { --a0: #7aa2ff; --a1: #3cc6c8; --a2: #f08a54; --a3: #b18cf0; --a4: #e3b05a; --a5: #4cc27f; --a6: #ff7a6b; --a7: #9ab3d1; } }
.a0 { --ac: var(--a0); } .a1 { --ac: var(--a1); } .a2 { --ac: var(--a2); } .a3 { --ac: var(--a3); }
.a4 { --ac: var(--a4); } .a5 { --ac: var(--a5); } .a6 { --ac: var(--a6); } .a7 { --ac: var(--a7); }
main .wrap.wide { max-width: 1320px; }
.mhead { display: grid; grid-template-columns: auto 1fr auto; gap: 18px; align-items: center; }
.mh-prog { display: flex; gap: 12px; align-items: center; }
.mh-next .chips { margin-top: 4px; }
.mh-tools { display: flex; flex-direction: column; gap: 6px; min-width: 200px; }
.nchip.next { border-color: color-mix(in srgb, var(--accent) 45%, var(--line)); background: color-mix(in srgb, var(--accent-soft) 60%, var(--surface)); cursor: pointer; font: inherit; font-size: .85rem; }
button.nchip { cursor: pointer; font: inherit; font-size: .85rem; }
.pring .bg { fill: none; stroke: var(--m-none); stroke-width: 7; } .pring .fg { fill: none; stroke: var(--m-mastered); stroke-width: 7; stroke-linecap: round; transition: stroke-dasharray .6s; }
.pring text { font-size: 14px; font-weight: 700; fill: var(--ink); }
.band-nav { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; margin: 2px 0 10px; }
.bchip { border: 1px solid var(--line); background: var(--surface); border-radius: 99px; padding: 4px 10px; cursor: pointer; font: inherit; font-size: .84rem; color: var(--ink); display: inline-flex; align-items: center; gap: 7px; }
.bchip:hover { border-color: var(--accent); } .bchip.me { border-color: var(--accent); color: var(--accent); font-weight: 600; }
.band-nav .bn-hint { margin-left: auto; }
.mini { display: inline-block; width: 38px; height: 5px; border-radius: 9px; background: var(--m-none); overflow: hidden; vertical-align: middle; }
.mini i { display: block; height: 100%; background: var(--m-mastered); }
.lmap-wrap { position: relative; }
.lmap-wrap.scroll { overflow-x: auto; -webkit-overflow-scrolling: touch; padding-bottom: 6px; }
.lmap { position: relative; margin: 0 auto; }
.lanes-head { display: grid; position: sticky; top: var(--hdr); z-index: 4; background: color-mix(in srgb, var(--bg) 92%, transparent);
  backdrop-filter: blur(6px); border-bottom: 1px solid var(--line); }
.lmap-wrap.scroll .lanes-head { position: relative; top: 0; }
.lane-title { display: flex; align-items: center; gap: 7px; padding: 9px 10px; font-size: .8rem; font-weight: 700; color: var(--ac); text-transform: uppercase; letter-spacing: .3px; line-height: 1.2; }
.lane-title i { width: 9px; height: 9px; border-radius: 3px; background: var(--ac); flex: none; }
.lmap-body { position: relative; }
.lband { position: absolute; left: 0; right: 0; border-radius: 14px; background: color-mix(in srgb, var(--surface) 70%, transparent); }
.lband.alt { background: color-mix(in srgb, var(--surface-2) 55%, transparent); }
.lband.olymp { background: color-mix(in srgb, var(--olymp) 7%, var(--surface)); }
.lband-head { display: flex; align-items: baseline; gap: 10px; padding: 12px 14px 0; font-size: .95rem; pointer-events: none; }
.lband-head b { font-size: 1.02rem; } .lband-head .muted { font-size: .82rem; }
.lband-prog { margin-left: auto; font-size: .78rem; color: var(--ink-3); display: inline-flex; gap: 6px; align-items: center; }
.ledges { position: absolute; left: 0; top: 0; pointer-events: none; overflow: visible; }
.ledge { fill: none; stroke: var(--ac); stroke-width: 1.3; opacity: .22; transition: opacity .15s; }
.ledge.hot { stroke: var(--accent); stroke-width: 2.4; opacity: .95; } .ledge.dim { opacity: .06; }
.lnode { position: absolute; display: flex; flex-direction: column; justify-content: center; text-align: left; padding: 6px 10px 9px 13px;
  border: 1px solid var(--line); border-radius: 11px; background: var(--surface); color: var(--ink); cursor: pointer; font: inherit;
  box-shadow: 0 1px 2px rgba(0,0,0,.05); overflow: hidden; transition: transform .12s, box-shadow .12s, opacity .15s, border-color .15s; }
.lnode::before { content: ""; position: absolute; left: 0; top: 0; bottom: 0; width: 4px; background: var(--ac); opacity: .85; }
.lnode:hover { transform: translateY(-1px); box-shadow: 0 4px 14px rgba(0,0,0,.10); border-color: var(--ac); z-index: 3; }
.lnode .lt { font-size: .78rem; line-height: 1.25; display: -webkit-box; -webkit-line-clamp: 3; -webkit-box-orient: vertical; overflow: hidden; }
.lnode .lm { position: absolute; left: 13px; right: 10px; bottom: 5px; height: 3px; border-radius: 3px; background: color-mix(in srgb, var(--m-none) 70%, transparent); overflow: hidden; }
.lnode .lm i { display: block; height: 100%; background: var(--m-mastered); }
.lnode .lstar { position: absolute; right: 6px; top: 3px; font-size: .72rem; color: var(--olymp); }
.lnode.m-learning { background: color-mix(in srgb, var(--m-learning) 15%, var(--surface)); } .lnode.m-learning .lm i { background: var(--m-learning); }
.lnode.m-proficient { background: color-mix(in srgb, var(--m-proficient) 26%, var(--surface)); }
.lnode.m-mastered { background: color-mix(in srgb, var(--m-mastered) 22%, var(--surface)); border-color: color-mix(in srgb, var(--m-mastered) 55%, var(--line)); }
.lnode.m-mastered .lt::after { content: " ✓"; color: var(--m-mastered); font-weight: 700; }
.lnode.m-inferred { border-style: dashed; border-color: color-mix(in srgb, var(--m-mastered) 60%, var(--line)); }
.lnode.olymp { border-color: color-mix(in srgb, var(--olymp) 40%, var(--line)); }
.lnode.next { box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 22%, transparent); border-color: var(--accent); }
.lnode.sel { border: 2px solid var(--accent); box-shadow: 0 0 0 4px color-mix(in srgb, var(--accent) 25%, transparent), 0 6px 18px rgba(0,0,0,.12); z-index: 4; }
.lnode.rel { border-color: var(--accent); } .lnode.dim { opacity: .32; } .lnode.faded { opacity: .22; } .lnode.hit { border: 2px solid var(--warn); }
.npanel-float { position: fixed; right: 18px; bottom: 18px; width: 390px; max-height: 72vh; overflow: auto; z-index: 30; }
.npanel-float .card { box-shadow: 0 10px 40px rgba(0,0,0,.18); border-color: var(--accent); }
.lane-pill { background: color-mix(in srgb, var(--ac) 14%, transparent); color: var(--ac); }
.lane-txt { color: var(--ac); }
@media (max-width: 900px) {
  .mhead { grid-template-columns: 1fr; } .mh-tools { min-width: 0; }
  .band-nav .bn-hint { display: none; }
  .npanel-float { left: 8px; right: 8px; bottom: 8px; width: auto; max-height: 58vh; }
}
@media (max-width: 760px) { :root { --hdr: 96px; } }
/* lessons (English) */
.keypoints { background: color-mix(in srgb, var(--accent-soft) 70%, var(--surface)); border-radius: 12px; padding: 10px 16px; margin: 12px 0; }
.keypoints ul { margin: 4px 0 0; padding-left: 18px; } .keypoints li .md p { margin: 2px 0; }
.ru-summary { border: 1px dashed var(--line); border-radius: 10px; padding: 8px 12px; margin: 10px 0; }
.ru-summary summary { cursor: pointer; font-weight: 600; font-size: .9rem; }
.mistakes { margin-top: 16px; } .mrow { border-top: 1px solid var(--line); padding: 8px 0; display: grid; grid-template-columns: 1fr 1fr; gap: 4px 14px; }
.mrow .mw { color: var(--bad); } .mrow .mw span { text-decoration: line-through; text-decoration-thickness: 1px; }
.mrow .mr { color: var(--ok); font-weight: 600; } .mrow .mwhy { grid-column: 1 / -1; color: var(--ink-2); } .mrow .mwhy p { margin: 0; }
@media (max-width: 600px) { .mrow { grid-template-columns: 1fr; } }
.speak { border: 0; background: transparent; cursor: pointer; font-size: 1rem; padding: 0 4px; line-height: 1; opacity: .75; }
.speak:hover { opacity: 1; } .speak.sm { font-size: .85rem; }
/* English answer inputs */
.gap-line { line-height: 2.2; font-size: 1.02rem; }
.gap-line .md, .gap-line .md p { display: inline; margin: 0; }
.gap-in { display: inline-block; min-width: 110px; width: auto; padding: 3px 8px !important; margin: 0 4px; border-radius: 7px; border-width: 1.5px !important;
  border-style: solid; font: inherit; vertical-align: baseline; }
.gap-in.ok { border-color: var(--ok) !important; background: var(--ok-soft); } .gap-in.bad { border-color: var(--bad) !important; background: var(--bad-soft); }
.ex-part { border: 1px solid var(--line); border-radius: 10px; padding: 10px 12px; }
.ex-part.ok { border-color: color-mix(in srgb, var(--ok) 50%, var(--line)); } .ex-part.missed { border-color: color-mix(in srgb, var(--bad) 50%, var(--line)); }
.ex-part .num { font-weight: 700; color: var(--ink-3); margin-right: 6px; }
.ex-fb { margin-top: 6px; font-size: .88rem; } .ex-show { margin-top: 6px; font-size: .92rem; } .ex-show p { margin: 0; }
.tokens { display: flex; flex-wrap: wrap; gap: 6px; }
.tok { border: 1px solid var(--line); background: var(--surface); border-radius: 8px; padding: 4px 10px; cursor: pointer; font: inherit; color: var(--ink); }
.tok:hover:not(:disabled) { border-color: var(--accent); } .tok.used { opacity: .35; } .tok:disabled { cursor: default; }
.order-line { min-height: 40px; border: 1.5px dashed var(--line); border-radius: 10px; padding: 6px; display: flex; flex-wrap: wrap; gap: 6px; align-items: center; margin-bottom: 8px; }
.order-line .tok { background: var(--accent-soft); border-color: color-mix(in srgb, var(--accent) 40%, var(--line)); }
.order-line .ph { color: var(--ink-3); font-size: .86rem; padding: 0 4px; }
/* writing */
.writing textarea { min-height: 260px; font: 1rem/1.6 var(--serif); }
.wstats { display: flex; flex-wrap: wrap; gap: 6px 14px; font-size: .85rem; color: var(--ink-2); }
.wstats b.ok { color: var(--ok); } .wstats b.bad { color: var(--bad); }
.phrases { display: flex; flex-wrap: wrap; gap: 6px; } .phrase { background: var(--surface-2); border-radius: 8px; padding: 3px 9px; font-size: .86rem; }
.checklist label { display: flex; gap: 8px; align-items: flex-start; padding: 4px 0; }
.model { border-left: 3px solid var(--ok); background: var(--ok-soft); border-radius: 0 10px 10px 0; padding: 10px 14px; font-family: var(--serif); white-space: pre-wrap; }
.mytext { font-family: var(--serif); white-space: pre-wrap; background: var(--surface-2); border-radius: 10px; padding: 10px 14px; }
/* vocabulary */
.vstats { display: grid; grid-template-columns: repeat(auto-fill, minmax(120px, 1fr)); gap: 10px; }
.vstat { background: var(--surface-2); border-radius: 12px; padding: 10px 12px; } .vstat b { display: block; font-size: 1.5rem; line-height: 1.1; }
.decks { display: grid; grid-template-columns: repeat(auto-fill, minmax(210px, 1fr)); gap: 10px; }
.deck { border: 1px solid var(--line); border-radius: 12px; padding: 10px 12px; display: flex; flex-direction: column; gap: 6px; background: var(--surface); color: var(--ink); }
.deck:hover { border-color: var(--accent); text-decoration: none; } .deck.cur { border-color: var(--accent); box-shadow: 0 0 0 3px var(--accent-soft); }
.deck .dt { font-weight: 600; } .deck .bar { height: 6px; background: var(--m-none); border-radius: 9px; overflow: hidden; display: flex; }
.deck .bar i { display: block; height: 100%; } .deck .bar .l { background: var(--m-proficient); } .deck .bar .m { background: var(--m-mastered); }
.level-h { display: flex; align-items: baseline; gap: 10px; margin: 6px 0 8px; } .level-h b { font-size: 1.3rem; }
.vcard { max-width: 620px; margin: 0 auto; text-align: center; padding: 26px 22px; }
.vcard .word { font-size: 2.2rem; font-weight: 700; letter-spacing: .2px; line-height: 1.2; }
.vcard .ipa { color: var(--ink-3); font-size: 1.05rem; } .vcard .pos { color: var(--ink-3); font-style: italic; font-size: .9rem; }
.vcard .tr { font-size: 1.3rem; margin-top: 8px; } .vcard .ex { font-family: var(--serif); font-size: 1.08rem; margin-top: 12px; }
.vcard .exr { color: var(--ink-3); font-size: .92rem; } .vcard .def { margin-top: 8px; color: var(--ink-2); } .vcard .note { margin-top: 8px; font-size: .88rem; color: var(--warn); }
.vopts { display: grid; grid-template-columns: 1fr 1fr; gap: 8px; margin-top: 16px; }
.vopt { border: 1.5px solid var(--line); background: var(--surface); border-radius: 12px; padding: 12px; cursor: pointer; font: inherit; color: var(--ink); }
.vopt:hover:not(:disabled) { border-color: var(--accent); } .vopt.right { border-color: var(--ok); background: var(--ok-soft); } .vopt.wrong { border-color: var(--bad); background: var(--bad-soft); }
.vin { font-size: 1.3rem; text-align: center; max-width: 360px; margin: 14px auto 0; display: block; }
.vgrades { display: flex; gap: 8px; justify-content: center; margin-top: 16px; flex-wrap: wrap; }
.vprog { height: 6px; border-radius: 9px; background: var(--m-none); overflow: hidden; } .vprog i { display: block; height: 100%; background: var(--accent); transition: width .3s; }
.big-speak { font-size: 2.4rem; border: 0; background: var(--accent-soft); width: 84px; height: 84px; border-radius: 50%; cursor: pointer; }
@media (max-width: 600px) { .vopts { grid-template-columns: 1fr; } .vcard .word { font-size: 1.8rem; } }
.wtable { width: 100%; border-collapse: collapse; } .wtable td { border-top: 1px solid var(--line); padding: 6px 6px; vertical-align: top; font-size: .9rem; }
.wtable td.w { font-weight: 600; white-space: nowrap; }
.ladder.six { grid-template-columns: repeat(6, 1fr); }
.mh-prog svg { flex: none; }

/* ===================== v0.4: constructivist design (red / black / paper + cobalt / yellow / pink) ===================== */
@font-face { font-family: "Oswald"; font-style: normal; font-display: swap; font-weight: 200 700;
  src: url(fonts/oswald-cyrillic-wght-normal.woff2) format("woff2-variations"), url(fonts/oswald-cyrillic-wght-normal.woff2) format("woff2");
  unicode-range: U+0301, U+0400-045F, U+0490-0491, U+04B0-04B1, U+2116; }
@font-face { font-family: "Oswald"; font-style: normal; font-display: swap; font-weight: 200 700;
  src: url(fonts/oswald-latin-ext-wght-normal.woff2) format("woff2-variations"), url(fonts/oswald-latin-ext-wght-normal.woff2) format("woff2");
  unicode-range: U+0100-02AF, U+0304, U+0308, U+0329, U+1E00-1E9F, U+1EF2-1EFF, U+2020, U+20A0-20AB, U+20AD-20C0, U+2113, U+2C60-2C7F, U+A720-A7FF; }
@font-face { font-family: "Oswald"; font-style: normal; font-display: swap; font-weight: 200 700;
  src: url(fonts/oswald-latin-wght-normal.woff2) format("woff2-variations"), url(fonts/oswald-latin-wght-normal.woff2) format("woff2");
  unicode-range: U+0000-00FF, U+0131, U+0152-0153, U+02BB-02BC, U+02C6, U+02DA, U+02DC, U+0304, U+0308, U+0329, U+2000-206F, U+2074, U+20AC, U+2122, U+2191, U+2193, U+2212, U+2215, U+FEFF, U+FFFD; }
:root {
  --display: "Oswald", "Arial Narrow", "Roboto Condensed", Impact, sans-serif;
  --bg: #f4ede1; --surface: #fffcf6; --surface-2: #f0e8da; --ink: #17161a; --ink-2: #4b4852; --ink-3: #827c84; --line: #e2d8c6;
  --accent: #2340c4; --accent-soft: #e3e8fb; --accent-ink: #ffffff;
  --red: #c8361f; --red-ink: #ffffff; --red-soft: #f7e0da; --yellow: #f2c230; --pink: #f3c6b8; --cream: #f7efe0; --black: #17161a; --sky: #7fa6e8;
  --radius: 4px; --shadow: 0 1px 0 rgba(23,22,26,.06);
  --a0: #2340c4; --a1: #0f7f81; --a2: #c8361f; --a3: #7a4bc2; --a4: #b07a10; --a5: #1f8a4c; --a6: #17161a; --a7: #4f6d8f;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #131215; --surface: #1c1b20; --surface-2: #25242b; --ink: #f2ece2; --ink-2: #bdb6c0; --ink-3: #8a848d; --line: #34323a;
    --accent: #8197ff; --accent-soft: #252c4d; --accent-ink: #0e1430;
    --red: #ff6448; --red-ink: #1a0a06; --red-soft: #3d2420; --cream: #2a2620; --black: #f2ece2;
    --a0: #8197ff; --a2: #ff7a5e; --a6: #d9d2c8;
  }
  .poster, .banner-art { filter: brightness(.9) saturate(.95); }
}
body { background: var(--bg); }
h1, h2, h3 { font-family: var(--display); font-weight: 600; letter-spacing: .2px; }
h1 { font-size: 1.85rem; } h2 { font-size: 1.3rem; } h3 { font-size: 1.08rem; }
.md h1, .md h2, .md h3, .lesson-body h3 { font-family: var(--font); letter-spacing: 0; }
.card > h2, .card > h3, .card > .row > h2, .card > .row > h3, .card > .row > div > h2 {
  text-transform: uppercase; letter-spacing: .6px; font-weight: 600; }
.card > h2, .card > .row > h2 { font-size: 1.12rem; } .card > h3, .card > .row > h3 { font-size: .98rem; }
.card > h2::before, .card > .row > h2::before { content: ""; display: inline-block; width: 10px; height: 10px; background: var(--red);
  margin-right: 9px; vertical-align: 2px; clip-path: polygon(0 0, 100% 0, 50% 100%); }
.card { border-radius: var(--radius); }
.pill { border-radius: 3px; } .btn { border-radius: 4px; } input[type=text], input[type=email], input[type=password], input[type=number], select, textarea { border-radius: 4px; }
.btn.primary { background: var(--red); border-color: var(--red); color: var(--red-ink); letter-spacing: .2px; }
.btn.primary:hover { filter: brightness(1.08); }
.btn.primary:focus-visible, .btn:focus-visible { outline: 3px solid var(--yellow); outline-offset: 1px; }
input:focus, select:focus, textarea:focus { border-color: var(--ink); box-shadow: 0 0 0 3px color-mix(in srgb, var(--yellow) 55%, transparent); }
a { color: var(--accent); }
/* header: paper strip with a heavy black rule, active item as a black block */
header.top { background: var(--bg); border-bottom: 3px solid var(--ink); }
header.top::after { content: ""; position: absolute; left: 0; bottom: -9px; height: 6px; width: 140px; background: var(--red); }
.brand { font-family: var(--display); font-weight: 700; text-transform: uppercase; letter-spacing: 2.5px; font-size: 1.22rem; }
nav.main a { color: var(--ink); font-weight: 500; border-radius: 2px; }
nav.main a:hover { background: var(--surface-2); }
nav.main a.on { background: var(--ink); color: var(--bg); font-weight: 600; }
.seg { border-color: var(--ink); border-radius: 3px; } .seg button.on { background: var(--ink); color: var(--bg); }
.lang-toggle { border-color: var(--ink); border-radius: 3px; }
.tabs { border-bottom: 2px solid var(--ink); }
.tabs a { color: var(--ink-2); font-weight: 500; } .tabs a.on { color: var(--ink); border-bottom: 4px solid var(--red); margin-bottom: -2px; }
/* page titles: a red wedge in front */
main h1:not(.card h1) { display: flex; align-items: center; gap: 12px; text-transform: uppercase; letter-spacing: .8px; }
main h1:not(.card h1)::before { content: ""; width: 22px; height: 22px; flex: none; background: var(--red); clip-path: polygon(0 0, 100% 0, 50% 100%); }
.notice { border-radius: 3px; border-left: 4px solid var(--accent); }
.notice.warn { border-left-color: var(--yellow); } .notice.ok { border-left-color: var(--ok); } .notice.bad { border-left-color: var(--red); }
.onboard { border: 2px solid var(--ink); background: linear-gradient(115deg, var(--yellow) 0 10px, var(--surface) 10px); padding-left: 26px; }
.pcard { border-radius: var(--radius); } .pcard:hover { border-color: var(--ink); box-shadow: 4px 4px 0 var(--red); transform: translate(-2px, -2px); }
.pcard { transition: transform .1s, box-shadow .1s; }
.big-num { font-family: var(--display); font-weight: 600; letter-spacing: 0; }
.ladder .step { border-radius: 2px; } .ladder .step.cur { outline: 2px solid var(--ink); background: var(--yellow); } .ladder .step.cur b { color: var(--black); }
.ladder .step.done { background: color-mix(in srgb, var(--red) 16%, var(--surface)); } .ladder .bar { background: var(--red); }
@media (prefers-color-scheme: dark) { .ladder .step.cur { color: #17161a; } .ladder .step.cur span { color: #3a3a3a; } }
/* footer: black poster strip */
.foot { background: #17161a; color: #f7efe0; margin-top: 30px; padding: 22px 16px 26px; display: flex; gap: 12px; align-items: center; justify-content: center;
  font-family: var(--display); text-transform: uppercase; letter-spacing: 2px; font-size: .8rem; border-top: 6px solid var(--red); }
.foot .muted { color: #a59d92; }
/* login: poster + form */
.auth2 { min-height: 100vh; display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(360px, 520px); background: var(--bg); }
.auth2 .poster-side { position: relative; overflow: hidden; background: var(--pink); border-right: 3px solid var(--ink); }
.auth2 .poster { width: 100%; height: 100%; display: block; position: absolute; inset: 0; }
.auth2 .form-side { padding: 7vh 40px 40px; display: flex; flex-direction: column; justify-content: center; }
.auth2 .brand { font-size: 1.9rem; letter-spacing: 4px; }
.auth2 .lead { font-family: var(--display); text-transform: uppercase; letter-spacing: 1px; font-size: 1.05rem; color: var(--ink-2); margin: 6px 0 18px; }
.auth2 form.card { border: 2px solid var(--ink); box-shadow: 8px 8px 0 var(--ink); padding: 20px 22px; }
.auth2 form.card > h2::before { display: none; }
.pt { font-family: var(--display); font-weight: 600; }
@media (max-width: 860px) {
  .auth2 { grid-template-columns: 1fr; min-height: 0; }
  .auth2 .poster-side { height: 250px; border-right: 0; border-bottom: 3px solid var(--ink); }
  .auth2 .form-side { padding: 22px 16px 40px; justify-content: flex-start; }
}
/* dashboard hero banner */
.banner { position: relative; overflow: hidden; border: 2px solid var(--ink); border-radius: var(--radius); background: var(--surface); min-height: 210px;
  display: flex; align-items: stretch; box-shadow: 6px 6px 0 var(--ink); }
.banner .banner-art { position: absolute; right: 0; top: 0; height: 100%; width: 62%; }
.banner .b-text { position: relative; z-index: 1; padding: 20px 22px; width: 48%; min-width: 300px; display: flex; flex-direction: column; gap: 8px; justify-content: center;
  background: linear-gradient(90deg, var(--surface) 82%, transparent); }
.banner .b-kicker { font-family: var(--display); text-transform: uppercase; letter-spacing: 2px; font-size: .82rem; color: var(--red); font-weight: 600; }
.banner .b-title { font-family: var(--display); text-transform: uppercase; font-weight: 700; font-size: 2.6rem; line-height: 1; letter-spacing: 1px; margin: 0; }
.banner .b-sub { color: var(--ink-2); font-size: .95rem; }
.banner .b-sub b { color: var(--ink); }
.banner .row { margin-top: 4px; }
@media (max-width: 760px) {
  .banner { flex-direction: column; min-height: 0; box-shadow: 4px 4px 0 var(--ink); }
  .banner .banner-art { position: relative; width: 100%; height: 130px; order: -1; }
  .banner .b-text { width: 100%; min-width: 0; background: var(--surface); padding: 14px 16px 16px; }
  .banner .b-title { font-size: 2rem; }
}
/* knowledge map in the new style */
.lane-title { font-family: var(--display); font-weight: 600; letter-spacing: .8px; font-size: .86rem; }
.lband-head b { font-family: var(--display); font-weight: 700; font-size: 1.25rem; text-transform: uppercase; letter-spacing: 1px; }
.lband { border-radius: 4px; }
.lnode { border-radius: 4px; } .lnode::before { width: 5px; }
.lnode.next { box-shadow: 3px 3px 0 var(--red); border-color: var(--ink); }
.lnode.sel { border: 2px solid var(--ink); box-shadow: 5px 5px 0 var(--red); }
.bchip, .nchip { border-radius: 3px; } .bchip.me { border-color: var(--ink); color: var(--ink); background: var(--yellow); }
.npanel-float .card { border: 2px solid var(--ink); box-shadow: 8px 8px 0 var(--red); }
.pring .fg { stroke: var(--red); } .pring text { font-family: var(--display); }
.mini i, .lnode .lm i { background: var(--red); }
/* lessons & English */
.keypoints { border-radius: 3px; background: color-mix(in srgb, var(--yellow) 22%, var(--surface)); border-left: 5px solid var(--yellow); }
.example { border-left-color: var(--red); background: color-mix(in srgb, var(--pink) 30%, var(--surface)); border-radius: 0 4px 4px 0; }
.vcard .word { font-family: var(--display); font-weight: 600; letter-spacing: .5px; font-size: 2.6rem; }
.vcard { border: 2px solid var(--ink); box-shadow: 6px 6px 0 var(--ink); }
.vstat { border-radius: 3px; } .vstat b { font-family: var(--display); font-weight: 600; }
.deck { border-radius: 4px; } .deck.cur { border-color: var(--ink); box-shadow: 4px 4px 0 var(--yellow); }
.deck .bar .m { background: var(--red); }
.level-h b { font-family: var(--display); font-size: 1.6rem; }
.vprog i { background: var(--red); }
.choice, .vopt, .tok, .ex-part, .gap-in { border-radius: 4px !important; }
.score-ring { font-family: var(--display); }
.done-art { display: flex; justify-content: center; }

/* ===================== v0.5: levels, clickable sections, readable map ===================== */
/* header: icons for the other subjects, the active one with its name; nothing gets cut */
header.top .wrap { max-width: 1440px; }
.seg.sm .seg-lab { display: none; }
.seg.sm button.on .seg-lab { display: inline; }
@media (max-width: 1150px) { .seg.sm button.on .seg-lab { display: none; } }
@media (max-width: 1400px) { .user-name { display: none; } }
nav.main { min-width: 0; }
/* ladder steps are links */
a.step { text-decoration: none; color: inherit; cursor: pointer; transition: transform .1s, box-shadow .1s; }
a.step:hover { text-decoration: none; transform: translate(-1px, -1px); box-shadow: 3px 3px 0 var(--ink); }
.ladder .step span { display: block; margin-top: 2px; }
.lvl-next { margin-top: 8px; color: var(--ink-2); }
/* clickable section bars */
.bars a.b { color: var(--ink); border-radius: 3px; padding: 2px 4px; margin: 2px -4px; }
.bars a.b:hover { background: var(--surface-2); text-decoration: none; }
.bars a.b .go { color: var(--red); opacity: 0; transition: opacity .1s; } .bars a.b:hover .go { opacity: 1; }
.bars .b { grid-template-columns: 150px 1fr 64px; }
/* level page */
.lvl-strip { display: flex; flex-wrap: wrap; gap: 6px; }
.lchip { border: 1.5px solid var(--line); border-radius: 3px; padding: 4px 12px; font-family: var(--display); font-weight: 600; color: var(--ink); background: var(--surface); }
.lchip:hover { border-color: var(--ink); text-decoration: none; } .lchip.done { background: color-mix(in srgb, var(--ok) 12%, var(--surface)); }
.lchip.me { border-color: var(--ink); } .lchip.me i { color: var(--red); font-style: normal; }
.lchip.on { background: var(--ink); color: var(--bg); border-color: var(--ink); }
h1.lvl-title { margin: 4px 0 0; text-transform: uppercase; letter-spacing: .6px; }
.achip { border: 1px solid var(--line); background: var(--surface); border-radius: 3px; padding: 3px 10px; font: inherit; font-size: .85rem; cursor: pointer; color: var(--ink); }
.achip:hover { border-color: var(--ink); } .achip.on { background: var(--ink); color: var(--bg); border-color: var(--ink); }
.achip[class*=" a"]:not(.on) { border-left: 4px solid var(--ac); }
.nchip.st-mastered, .nchip.st-proficient, .nchip.st-inferred { border-color: color-mix(in srgb, var(--ok) 55%, var(--line)); background: color-mix(in srgb, var(--ok) 10%, var(--surface)); }
/* map: status badges */
.lnode { justify-content: space-between; padding: 7px 10px 6px 13px; }
.lnode .lfoot { display: flex; align-items: center; gap: 8px; min-height: 14px; }
.lnode .lm { position: static; flex: 1; height: 3px; }
.lnode .lbadge { font-size: .68rem; font-weight: 700; letter-spacing: .2px; white-space: nowrap; }
.lnode.s-known { background: color-mix(in srgb, var(--ok) 20%, var(--surface)); border-color: color-mix(in srgb, var(--ok) 65%, var(--line)); }
.lnode.s-known .lbadge { color: var(--ok); } .lnode.s-known .lm i { background: var(--ok); }
.lnode.m-inferred.s-known { background: color-mix(in srgb, var(--ok) 9%, var(--surface)); border-style: dashed; }
.lnode.m-mastered .lt::after { content: none; }
.lnode.s-learning { background: color-mix(in srgb, var(--yellow) 22%, var(--surface)); border-color: color-mix(in srgb, var(--yellow) 80%, var(--line)); }
.lnode.s-learning .lbadge { color: #8a6200; } .lnode.s-learning .lm i { background: var(--yellow); }
.lnode.s-ready { border: 1.5px solid var(--ink); } .lnode.s-ready .lbadge { color: var(--red); }
.lnode.s-later { background: var(--surface); } .lnode.s-later .lt { color: var(--ink-2); }
@media (prefers-color-scheme: dark) { .lnode.s-learning .lbadge { color: var(--yellow); } }
.lnode.hl-off { opacity: .2; } .lnode.hl-on { box-shadow: 3px 3px 0 var(--ink); z-index: 2; }
.lnode.inchain { border-color: var(--accent); }
.lnode.dim { opacity: .28; } .lnode.dim.hl-on { opacity: .6; }
/* map: arrows */
.ledge { opacity: 1; stroke-width: 1.6; fill: none; }
.ledge.in { stroke: var(--accent); stroke-width: 2.2; }
.ledge.out { stroke: var(--red); stroke-width: 2; stroke-dasharray: 6 4; }
.ledge.all { stroke: var(--ink-3); opacity: .35; stroke-width: 1.2; }
.ledge.dim { stroke: var(--ink-3); opacity: .08; }
.arrow.in { fill: var(--accent); } .arrow.out { fill: var(--red); } .arrow.all { fill: var(--ink-3); }
/* map: tools and legend */
.map-tools { display: flex; flex-wrap: wrap; gap: 8px 18px; align-items: center; margin: 0 0 8px; }
.hl-seg button { font-size: .82rem; padding: 4px 9px; } .hl-seg button b { font-weight: 600; opacity: .7; margin-left: 2px; }
.map-legend { border: 1px dashed var(--line); border-radius: 4px; padding: 6px 12px; margin-bottom: 10px; background: var(--surface); }
.map-legend summary { cursor: pointer; }
.legend-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(330px, 1fr)); gap: 6px 18px; margin-top: 8px; color: var(--ink-2); }
.lg-node { display: inline-block; min-width: 92px; border: 1px solid var(--line); border-radius: 3px; padding: 1px 6px; font-size: .72rem; font-weight: 700; margin-right: 6px; }
.lg-node.s-known { color: var(--ok); background: color-mix(in srgb, var(--ok) 20%, var(--surface)); border-color: color-mix(in srgb, var(--ok) 65%, var(--line)); }
.lg-node.s-learning { color: #8a6200; background: color-mix(in srgb, var(--yellow) 22%, var(--surface)); }
.lg-node.s-ready { color: var(--red); border: 1.5px solid var(--ink); } .lg-node.s-later { color: var(--ink-3); }
.lg-in, .lg-out { display: inline-block; width: 34px; height: 0; border-top: 2.5px solid var(--accent); vertical-align: middle; margin-right: 6px; position: relative; }
.lg-out { border-top: 2.5px dashed var(--red); }
.lg-in::after, .lg-out::after { content: ""; position: absolute; right: -2px; top: -6px; border: 5px solid transparent; border-left: 7px solid var(--accent); }
.lg-out::after { border-left-color: var(--red); }
/* node panel: path to the topic */
.path-box { border-left: 4px solid var(--accent); background: color-mix(in srgb, var(--accent-soft) 60%, var(--surface)); padding: 8px 10px; border-radius: 0 4px 4px 0; }
ol.path { margin: 6px 0 0; padding-left: 22px; } ol.path li { margin: 3px 0; }
.linkish { border: 0; background: none; padding: 0; color: var(--ink); font: inherit; cursor: pointer; display: inline-flex; gap: 6px; align-items: center; text-align: left; }
.linkish:hover { color: var(--accent); text-decoration: underline; }
.hl-seg .h-learning:not(.on) { color: #8a6200; } .hl-seg .h-known:not(.on) { color: var(--ok); } .hl-seg .h-ready:not(.on) { color: var(--red); }

/* ===================== v0.6: Maths for kids — playful mode ===================== */
.pill.puzzle { background: var(--yellow); color: var(--black); border-color: var(--yellow); }
.ladder.eight { grid-template-columns: repeat(4, 1fr); }
.kfig { margin: 12px 0 4px; display: flex; justify-content: center; }
.kfig svg { width: 100%; max-width: 460px; height: auto; max-height: 340px; background: #fffdf8; border-radius: 10px; }
.kfig.lesson-fig svg { max-width: 520px; }
@media (prefers-color-scheme: dark) { .kfig svg { background: #f7efe0; } }
/* stars */
.stars { display: inline-flex; gap: 1px; font-size: 1.05rem; line-height: 1; white-space: nowrap; }
.stars i { font-style: normal; color: color-mix(in srgb, var(--ink-3) 45%, transparent); }
.stars i.on { color: var(--yellow); text-shadow: 0 0 0 #b98a00, 0 1px 0 #b98a00; }
.stars.big { font-size: 2rem; gap: 4px; }
.stars.big i.on { animation: kpop .5s cubic-bezier(.3,1.6,.5,1) both; }
.stars.big i:nth-child(2) { animation-delay: .15s; } .stars.big i:nth-child(3) { animation-delay: .3s; }
@keyframes kpop { from { transform: scale(0) rotate(-40deg); } to { transform: scale(1) rotate(0); } }
/* mascot */
.nabla { color: var(--ink); flex: none; overflow: visible; }
.nabla .ball { animation: kbounce 1.6s ease-in-out infinite; transform-origin: 108px 104px; }
.nabla.hello .arm-r { animation: kwave 1.4s ease-in-out infinite; transform-origin: 92px 44px; }
.nabla.cheer { animation: kjump .9s ease-in-out 2; }
.nabla.cheer .spark { animation: ktwinkle 1s ease-in-out infinite; transform-origin: 60px 10px; }
@keyframes kbounce { 0%, 100% { transform: translateY(0); } 50% { transform: translateY(-7px); } }
@keyframes kwave { 0%, 100% { transform: rotate(0); } 25% { transform: rotate(-14deg); } 75% { transform: rotate(10deg); } }
@keyframes kjump { 0%, 100% { transform: translateY(0); } 40% { transform: translateY(-14px); } }
@keyframes ktwinkle { 0%, 100% { transform: scale(1); opacity: 1; } 50% { transform: scale(.6); opacity: .6; } }
@media (prefers-reduced-motion: reduce) { .nabla *, .nabla, .stars i, .confetti i { animation: none !important; } }
.say { display: flex; align-items: flex-end; gap: 10px; }
.say .bubble { position: relative; background: var(--surface); border: 2px solid var(--ink); border-radius: 18px; padding: 12px 16px; font-size: 1.05rem;
  box-shadow: 4px 4px 0 var(--ink); max-width: 640px; margin-bottom: 26px; }
.say .bubble::before { content: ""; position: absolute; left: -12px; bottom: 16px; width: 18px; height: 18px; background: var(--surface);
  border-left: 2px solid var(--ink); border-bottom: 2px solid var(--ink); transform: rotate(45deg) skew(8deg, 8deg); }
.say .bubble .md p { margin: .2em 0; }
.say.fact { margin-top: 14px; } .say.fact .bubble { background: color-mix(in srgb, var(--yellow) 22%, var(--surface)); }
.say.fact .bubble::before { background: color-mix(in srgb, var(--yellow) 22%, var(--surface)); }
.say.result .bubble { border-color: var(--red); box-shadow: 4px 4px 0 var(--red); }
.k-hi { font-family: var(--display); font-size: 1.6rem; font-weight: 600; line-height: 1.15; margin-bottom: 2px; }
/* confetti */
.confetti { position: fixed; inset: 0; pointer-events: none; z-index: 50; overflow: hidden; }
.confetti i { position: absolute; top: -20px; animation-name: kfall; animation-timing-function: cubic-bezier(.25,.6,.45,1); animation-fill-mode: forwards; }
@keyframes kfall { to { transform: translate(var(--dx), 105vh) rotate(var(--r)); } }
/* kids theme: bigger, rounder, softer */
body.kids { font-size: 17px; }
body.kids .card { border-radius: 16px; }
body.kids .btn { border-radius: 12px; }
body.kids .btn.big { padding: 12px 20px; font-size: 1.08rem; }
body.kids .pill { border-radius: 999px; }
body.kids nav.main a { font-size: 1rem; border-radius: 12px; }
body.kids h1 { font-size: 2rem; }
body.kids .pcard, body.kids .choice { border-radius: 14px; }
body.kids .lesson-body, body.kids .statement { font-size: 1.08rem; }
.kcard h2::before { border-radius: 50%; }
.khero { display: grid; grid-template-columns: minmax(0, 1fr) auto; gap: 16px; align-items: end; padding: 18px 20px 8px; border: 2px solid var(--ink);
  border-radius: 20px; background: linear-gradient(120deg, var(--pink) 0%, color-mix(in srgb, var(--pink) 40%, var(--surface)) 55%, var(--surface) 100%);
  box-shadow: 6px 6px 0 var(--ink); }
.khero .say .bubble { margin-bottom: 30px; }
.kstats { display: grid; grid-template-columns: repeat(2, minmax(110px, 1fr)); gap: 8px; padding-bottom: 12px; }
.kstat { display: flex; flex-direction: column; background: var(--surface); border: 2px solid var(--ink); border-radius: 14px; padding: 8px 12px; color: var(--ink); }
.kstat b { font-family: var(--display); font-size: 1.35rem; line-height: 1.2; } .kstat span { font-size: .82rem; color: var(--ink-2); }
a.kstat:hover { text-decoration: none; transform: translate(-1px, -1px); box-shadow: 3px 3px 0 var(--red); }
@media (max-width: 760px) { .khero { grid-template-columns: 1fr; } .kstats { grid-template-columns: repeat(4, 1fr); } .kstat b { font-size: 1.1rem; } }
@media (max-width: 480px) { .kstats { grid-template-columns: repeat(2, 1fr); } .say .nabla { width: 70px; height: 76px; } .k-hi { font-size: 1.3rem; } }
.kplace { display: flex; justify-content: space-between; align-items: center; gap: 14px; flex-wrap: wrap; border: 2px solid var(--red); }
.kplace p { margin: 4px 0 0; }
/* level path */
.kpath { display: grid; grid-template-columns: repeat(8, 1fr); gap: 4px; margin: 10px 0 8px; position: relative; }
.kpath::before { content: ""; position: absolute; left: 6%; right: 6%; top: 25px; border-top: 4px dashed var(--line); }
.kstone { position: relative; display: flex; flex-direction: column; align-items: center; text-align: center; color: var(--ink-2); gap: 2px; }
.kstone:hover { text-decoration: none; }
.kstone .dot { width: 52px; height: 52px; border-radius: 50%; display: grid; place-items: center; background: var(--surface-2); border: 3px solid var(--line);
  font-family: var(--display); font-weight: 700; font-size: 1.15rem; color: var(--ink-3); overflow: visible; }
.kstone b { font-size: .8rem; line-height: 1.15; } .kstone i { font-style: normal; font-size: .7rem; color: var(--ink-3); }
.kstone.done .dot { background: var(--yellow); border-color: var(--ink); color: var(--black); }
.kstone.cur .dot { background: var(--surface); border-color: var(--red); box-shadow: 0 0 0 4px var(--red-soft); }
.kstone.cur .dot .nabla { margin-top: 4px; }
.kstone.cur b { color: var(--red); }
@media (max-width: 700px) { .kpath { grid-template-columns: repeat(4, 1fr); row-gap: 12px; } .kpath::before { display: none; } }
.kprog .track, .kcard .track, .klvrow .track { height: 10px; background: var(--surface-2); border-radius: 999px; overflow: hidden; border: 1px solid var(--line); }
.kprog .fill, .kcard .fill, .klvrow .fill { height: 100%; background: linear-gradient(90deg, var(--yellow), var(--red)); border-radius: 999px; }
.kprog .small { margin-top: 6px; }
.track.sm { height: 6px; }
/* problem cards */
.kplist { display: grid; gap: 8px; } .kgrid { display: grid; grid-template-columns: repeat(auto-fill, minmax(320px, 1fr)); gap: 10px; }
.kpc { display: grid; grid-template-columns: auto 1fr auto; grid-template-rows: auto auto; gap: 2px 12px; align-items: center; padding: 12px 14px;
  background: var(--surface); border: 2px solid var(--line); border-radius: 16px; color: var(--ink); transition: transform .1s, box-shadow .1s; }
.kpc:hover { text-decoration: none; border-color: var(--ink); transform: translate(-2px, -2px); box-shadow: 4px 4px 0 var(--accent); }
.kpc.puzzle:hover { box-shadow: 4px 4px 0 var(--yellow); }
.kpc-ico { grid-row: span 2; width: 42px; height: 42px; border-radius: 12px; display: grid; place-items: center; background: var(--accent-soft); font-size: 1.25rem; }
.kpc.puzzle .kpc-ico { background: color-mix(in srgb, var(--yellow) 35%, var(--surface)); }
.kpc.solved .kpc-ico { background: var(--ok-soft); }
.kpc-t { font-weight: 600; line-height: 1.25; } .kpc-meta { font-size: .8rem; color: var(--ink-3); grid-column: 2; }
.kpc-st { grid-row: 1 / span 2; grid-column: 3; }
/* catalogue chips */
.kchips { display: flex; flex-wrap: wrap; gap: 6px; align-items: center; }
.kchips .lab { font-size: .85rem; color: var(--ink-3); margin-right: 4px; }
.kchip { border: 2px solid var(--line); background: var(--surface); border-radius: 999px; padding: 4px 12px; cursor: pointer; font-size: .9rem; color: var(--ink-2); }
.kchip:hover { border-color: var(--ink); } .kchip.on { background: var(--ink); border-color: var(--ink); color: var(--bg); }
/* problem page */
.kprob { max-width: 860px; margin: 0 auto; }
.kstatement h1 { margin: 6px 0 8px; } .kpills { gap: 6px; }
.kanswer { display: flex; flex-direction: column; gap: 14px; }
.kpart { border-radius: 14px; } .kpart.ok .kinp input { border-color: var(--ok); background: var(--ok-soft); }
.kpart.bad .kinp input { border-color: var(--bad); animation: kshake .35s; } .kpart.missed .kinp input { border-color: var(--bad); }
@keyframes kshake { 25% { transform: translateX(-6px); } 50% { transform: translateX(6px); } 75% { transform: translateX(-3px); } }
.kprompt { font-weight: 600; margin-bottom: 6px; }
.kinp { display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
.kinp input { width: 190px !important; font-size: 1.6rem; font-family: var(--display); text-align: center; padding: 8px 12px; border: 3px solid var(--ink) !important; border-radius: 14px !important; }
.kunit { font-size: 1.2rem; font-weight: 600; } .kok { color: var(--ok); font-size: 1.6rem; font-weight: 700; } .kno { color: var(--bad); font-size: 1.6rem; font-weight: 700; }
body.kids .choice, .kanswer .choice { padding: 12px 14px; font-size: 1.05rem; border-width: 2px; }
.kanswer .choices { grid-template-columns: repeat(auto-fill, minmax(200px, 1fr)); gap: 8px; }
.kstarsbig { margin-top: 6px; }
.khint { display: flex; gap: 8px; align-items: flex-start; } .khint .md p { margin: 0; } .khint + .khint { margin-top: 8px; }
.kmaplink { display: flex; align-items: center; gap: 14px; color: var(--ink); } .kmaplink:hover { text-decoration: none; border-color: var(--ink); }
.krecent { display: flex; justify-content: space-between; gap: 10px; padding: 6px 0; border-bottom: 1px dashed var(--line); color: var(--ink); }
.krecent:last-child { border-bottom: 0; } .krecent:hover { text-decoration: none; color: var(--red); }
/* badges */
.kbadges { display: grid; grid-template-columns: repeat(auto-fill, minmax(150px, 1fr)); gap: 10px; }
.kbadges.sm { display: flex; flex-wrap: wrap; gap: 6px; }
.kbcell { display: flex; flex-direction: column; gap: 4px; padding: 10px; border: 2px dashed var(--line); border-radius: 14px; }
.kbcell.on { border-style: solid; border-color: var(--ink); background: color-mix(in srgb, var(--yellow) 14%, var(--surface)); }
.kbadge { display: inline-flex; align-items: center; gap: 8px; filter: grayscale(1); opacity: .55; }
.kbadge.on { filter: none; opacity: 1; }
.kbadge .medal { width: 40px; height: 40px; border-radius: 50%; display: grid; place-items: center; background: var(--yellow); color: var(--black);
  border: 3px solid var(--ink); font-family: var(--display); font-weight: 700; font-size: .95rem; flex: none; }
.kbadge.on .medal { box-shadow: 0 0 0 3px var(--red-soft); }
.kbadge .bname { font-weight: 600; font-size: .9rem; line-height: 1.2; }
.kbadges.sm .kbadge .medal { width: 30px; height: 30px; font-size: .75rem; border-width: 2px; }
.kbadge-row { display: flex; gap: 12px; align-items: center; }
.klvrow { display: grid; grid-template-columns: 26px 110px 1fr auto; gap: 10px; align-items: center; padding: 5px 0; color: var(--ink); }
.klvrow:hover { text-decoration: none; } .klvrow .lv { font-family: var(--display); font-weight: 700; color: var(--red); } .klvrow .nm { font-size: .9rem; }
/* lessons */
.keypoints.kid { border: 2px solid var(--ink); border-radius: 14px; padding: 10px 14px; background: color-mix(in srgb, var(--accent) 7%, var(--surface)); margin-top: 12px; }
.keypoints.kid .kp-h { font-family: var(--display); font-weight: 600; font-size: 1.05rem; }
.keypoints.kid ul { margin: 6px 0 0; padding-left: 20px; } .keypoints.kid li .md p { margin: 2px 0; }