@import url('https://fonts.googleapis.com/css2?family=Manrope:wght@500;600;700;800&family=JetBrains+Mono:wght@500;600;700&display=swap');
:root{--bg:#070a12;--ink:#e9f1ff;--muted:#8ea3c4;}
*{margin:0;padding:0;box-sizing:border-box;}
html,body{background:var(--bg);}
body{font-family:'Manrope',system-ui,sans-serif;color:var(--ink);min-height:100vh;position:relative;overflow-x:hidden;padding-bottom:90px;}
body::before{content:'';position:fixed;inset:0;z-index:0;pointer-events:none;
  background-image:linear-gradient(rgba(120,160,220,.05) 1px,transparent 1px),linear-gradient(90deg,rgba(120,160,220,.05) 1px,transparent 1px);
  background-size:46px 46px;
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body::after{content:'';position:fixed;inset:0;z-index:0;pointer-events:none;
  background:radial-gradient(55% 36% at 50% 0%,var(--accent),transparent 70%);opacity:.12;}
.wrap{position:relative;z-index:2;max-width:800px;margin:0 auto;padding:0 24px;}

.top{display:flex;align-items:center;justify-content:space-between;padding:26px 0 0;gap:12px;}
.back{display:inline-flex;align-items:center;gap:9px;color:var(--muted);text-decoration:none;font-weight:600;font-size:14px;
  padding:9px 16px;border:1px solid rgba(140,170,220,.16);border-radius:999px;background:rgba(13,20,34,.6);transition:.2s;}
.back:hover{color:var(--ink);border-color:var(--accent);box-shadow:0 0 0 3px color-mix(in oklch,var(--accent) 14%,transparent);}
.back svg{width:16px;height:16px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;}
.idx{font-family:'JetBrains Mono',monospace;font-size:12px;letter-spacing:.2em;color:var(--accent);opacity:.8;white-space:nowrap;}

.hero{display:flex;align-items:center;gap:24px;margin-top:42px;}
.emb{flex:none;width:92px;height:92px;border-radius:22px;display:grid;place-items:center;
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  background:radial-gradient(120% 120% at 30% 20%,color-mix(in oklch,var(--accent) 18%,#0b1220),#0b1220);
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.emb svg{width:46px;height:46px;fill:none;stroke:var(--accent);stroke-width:1.7;stroke-linecap:round;stroke-linejoin:round;}
.htxt{flex:1;min-width:0;}
.htxt .label{font-family:'JetBrains Mono',monospace;font-size:12px;font-weight:600;letter-spacing:.24em;color:var(--accent);text-transform:uppercase;}
.htxt h1{font-size:clamp(24px,4vw,34px);font-weight:800;letter-spacing:-.01em;line-height:1.12;margin-top:9px;overflow-wrap:break-word;
  background:linear-gradient(92deg,var(--ink),color-mix(in oklch,var(--accent) 70%,var(--ink)));
  -webkit-background-clip:text;background-clip:text;color:transparent;padding-bottom:.06em;}
.htxt .sub{color:var(--muted);font-size:16px;font-weight:600;margin-top:9px;}
.rule{height:1px;margin:30px 0 28px;background:linear-gradient(90deg,var(--accent),transparent 70%);opacity:.5;}

.lead{font-size:18px;line-height:1.65;color:var(--ink);font-weight:500;}
.lead b{color:color-mix(in oklch,var(--accent) 72%,var(--ink));}

/* ── Section framing: clear THEORY vs PRACTICE divide ───────────── */
.sec{margin-top:30px;}
.zone-tab{display:inline-flex;align-items:center;gap:10px;padding:8px 16px 8px 12px;border-radius:999px;
  font-family:'JetBrains Mono',monospace;font-size:12px;font-weight:700;letter-spacing:.22em;text-transform:uppercase;}
.zone-tab svg{width:16px;height:16px;fill:none;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;}
/* theory tab: outlined / cool */
.theory .zone-tab{color:var(--accent);border:1px solid color-mix(in oklch,var(--accent) 42%,transparent);background:color-mix(in oklch,var(--accent) 9%,#0b1220);}
.theory .zone-tab svg{stroke:var(--accent);}
.sec h2{font-size:23px;font-weight:800;margin-top:16px;letter-spacing:-.01em;}
.sec h3{font-size:16px;font-weight:800;margin-top:24px;color:color-mix(in oklch,var(--accent) 55%,var(--ink));}

/* theory body */
.theory p{font-size:16.5px;line-height:1.7;color:#d2ddf0;margin-top:14px;}
.theory p b,.theory li b{color:#eaf1ff;font-weight:700;}
.term{color:color-mix(in oklch,var(--accent) 70%,var(--ink));font-weight:800;}

/* bullet list */
.blist{list-style:none;margin:16px 0 0;display:flex;flex-direction:column;gap:10px;}
.blist li{position:relative;padding-left:24px;font-size:16px;line-height:1.6;color:#d2ddf0;}
.blist li::before{content:'';position:absolute;left:4px;top:9px;width:7px;height:7px;border-radius:2px;
  background:var(--accent);transform:rotate(45deg);opacity:.85;}

/* definition / formula callout */
.def{margin-top:18px;padding:18px 20px;border-radius:14px;border:1px solid rgba(140,170,220,.14);
  border-left:3px solid var(--accent);background:rgba(13,20,34,.6);}
.def .def-term{display:block;font-weight:800;font-size:16px;color:color-mix(in oklch,var(--accent) 65%,var(--ink));margin-bottom:6px;}
.def p{margin-top:6px;}
.def p:first-child{margin-top:0;}

/* code / terminal / monospace block (formulas, commands, tables) */
.code{margin-top:18px;border-radius:14px;overflow:hidden;border:1px solid rgba(140,170,220,.16);
  background:#070b14;box-shadow:inset 0 0 0 1px rgba(0,0,0,.4);}
.code .code-bar{display:flex;align-items:center;gap:7px;padding:10px 14px;background:rgba(13,20,34,.85);border-bottom:1px solid rgba(140,170,220,.12);}
.code .code-bar .dt{width:9px;height:9px;border-radius:50%;background:rgba(140,170,220,.3);}
.code .code-bar .nm{margin-left:6px;font-family:'JetBrains Mono',monospace;font-size:11.5px;letter-spacing:.08em;color:var(--muted);}
.code pre{margin:0;padding:16px 18px;font-family:'JetBrains Mono',monospace;font-size:13.5px;line-height:1.75;
  color:#cfe0f5;overflow-x:auto;white-space:pre;}
.code pre .c{color:var(--muted);}             /* comment / dimmed */
.code pre .a{color:color-mix(in oklch,var(--accent) 72%,var(--ink));font-weight:600;}  /* accent token */
.code pre .g{color:oklch(0.82 0.13 150);}      /* green (output) */

/* highlighted note: Важно / Запомни / Признак */
.callout{margin-top:18px;display:flex;gap:14px;padding:16px 18px;border-radius:14px;
  background:color-mix(in oklch,var(--accent) 12%,#0b1220);border:1px solid color-mix(in oklch,var(--accent) 30%,transparent);}
.callout .ico{flex:none;width:30px;height:30px;border-radius:9px;display:grid;place-items:center;
  background:color-mix(in oklch,var(--accent) 22%,#0b1220);}
.callout .ico svg{width:17px;height:17px;fill:none;stroke:var(--accent);stroke-width:2;stroke-linecap:round;stroke-linejoin:round;}
.callout .ctxt{font-size:15px;line-height:1.6;color:#dbe6f6;}
.callout .ctxt b{color:color-mix(in oklch,var(--accent) 68%,var(--ink));font-weight:800;}

/* small inline tools list */
.tools{margin-top:16px;display:flex;flex-direction:column;gap:8px;}
.tools .tool{display:flex;align-items:baseline;gap:12px;font-size:14.5px;}
.tools .tool code{font-family:'JetBrains Mono',monospace;color:color-mix(in oklch,var(--accent) 70%,var(--ink));font-weight:600;}
.tools .tool span{color:var(--muted);}

/* ══ THEORY → PRACTICE divider ══════════════════════════════════ */
.divider{display:flex;align-items:center;gap:16px;margin:44px 0 0;}
.divider .ln{flex:1;height:1px;background:linear-gradient(90deg,transparent,rgba(140,170,220,.28));}
.divider .ln.r{background:linear-gradient(90deg,rgba(140,170,220,.28),transparent);}
.divider .dlabel{font-family:'JetBrains Mono',monospace;font-size:11px;font-weight:700;letter-spacing:.3em;color:var(--muted);text-transform:uppercase;white-space:nowrap;}

/* ══ PRACTICE — workbook / textbook sheet ══════════════════════ */
.practice{margin-top:26px;position:relative;border-radius:20px;padding:30px 28px 28px;
  background:
    repeating-linear-gradient(0deg,transparent 0 33px,rgba(140,170,220,.05) 33px 34px),
    linear-gradient(180deg,rgba(16,23,38,.92),rgba(11,17,30,.92));
  border:1px solid color-mix(in oklch,var(--accent) 26%,transparent);
  box-shadow:0 24px 60px rgba(0,0,0,.4),0 0 0 1px rgba(0,0,0,.3) inset;}
.practice::before{content:'';position:absolute;left:0;top:0;bottom:0;width:4px;border-radius:20px 0 0 20px;
  background:linear-gradient(180deg,var(--accent),color-mix(in oklch,var(--accent) 40%,transparent));}
.practice .zone-tab{color:#0a0f1a;background:var(--accent);border:none;
  box-shadow:0 6px 20px color-mix(in oklch,var(--accent) 35%,transparent);}
.practice .zone-tab svg{stroke:#0a0f1a;}
.practice h2{margin-top:14px;}
.practice .pintro{font-size:16px;line-height:1.6;color:#d2ddf0;margin-top:12px;}

/* numbered exercise */
.task{margin-top:22px;}
.task + .task{margin-top:26px;padding-top:24px;border-top:1px dashed rgba(140,170,220,.16);}
.task-no{display:inline-flex;align-items:center;gap:9px;font-family:'JetBrains Mono',monospace;
  font-size:13px;font-weight:700;letter-spacing:.06em;color:color-mix(in oklch,var(--accent) 65%,var(--ink));text-transform:uppercase;}
.task-no::before{content:'';width:22px;height:2px;background:var(--accent);border-radius:2px;}
.task-intro{font-size:15.5px;line-height:1.6;color:#d2ddf0;margin-top:8px;}

/* workbook step list (numbered circles) */
.steps{list-style:none;counter-reset:st;margin:14px 0 0;display:flex;flex-direction:column;gap:12px;}
.steps li{counter-increment:st;position:relative;padding:2px 0 2px 42px;font-size:15.5px;line-height:1.6;color:#dbe6f6;min-height:30px;}
.steps li::before{content:counter(st);position:absolute;left:0;top:0;width:28px;height:28px;border-radius:9px;
  display:grid;place-items:center;font-family:'JetBrains Mono',monospace;font-size:13px;font-weight:700;
  color:var(--accent);background:color-mix(in oklch,var(--accent) 14%,#0b1220);border:1px solid color-mix(in oklch,var(--accent) 34%,transparent);}
.steps li b{color:#fff;font-weight:700;}

/* checklist (☐) — for hands-on lab tasks */
.checks{list-style:none;margin:14px 0 0;display:flex;flex-direction:column;gap:11px;}
.checks li{position:relative;padding:3px 0 3px 38px;font-size:15.5px;line-height:1.6;color:#dbe6f6;}
.checks li::before{content:'';position:absolute;left:0;top:2px;width:22px;height:22px;border-radius:6px;
  border:2px solid color-mix(in oklch,var(--accent) 50%,transparent);background:rgba(7,11,20,.6);}
.checks li::after{content:'';position:absolute;left:7px;top:6px;width:9px;height:5px;border-left:2px solid var(--accent);
  border-bottom:2px solid var(--accent);transform:rotate(-45deg);opacity:.32;}
.checks li b{color:#fff;font-weight:700;}

/* inline code chips inside practice */
.practice code,.theory code,.lead code{font-family:'JetBrains Mono',monospace;font-size:.92em;
  background:rgba(7,11,20,.7);border:1px solid rgba(140,170,220,.16);border-radius:6px;padding:1px 7px;
  color:color-mix(in oklch,var(--accent) 60%,var(--ink));}

/* variant cards (Вариант А / Б) */
.variants{display:grid;grid-template-columns:1fr 1fr;gap:14px;margin-top:16px;}
.variant{border-radius:14px;border:1px solid rgba(140,170,220,.16);background:rgba(7,11,20,.5);overflow:hidden;}
.variant .vh{padding:9px 16px;font-family:'JetBrains Mono',monospace;font-size:12px;font-weight:700;letter-spacing:.14em;
  text-transform:uppercase;color:var(--accent);background:color-mix(in oklch,var(--accent) 12%,#0b1220);border-bottom:1px solid rgba(140,170,220,.14);}
.variant .vb{padding:14px 16px;}
.variant ol{margin:0;padding-left:18px;display:flex;flex-direction:column;gap:9px;}
.variant ol li{font-size:14.5px;line-height:1.55;color:#dbe6f6;}
.variant ol li::marker{color:var(--accent);font-family:'JetBrains Mono',monospace;font-weight:700;}
.variant ol li b{color:#fff;}
@media(max-width:620px){.variants{grid-template-columns:1fr;}}

/* teacher answer spoiler */
.answer{margin-top:18px;border-radius:12px;border:1px solid rgba(140,170,220,.18);background:rgba(7,11,20,.5);overflow:hidden;}
.answer summary{cursor:pointer;list-style:none;display:flex;align-items:center;gap:10px;padding:13px 16px;
  font-family:'JetBrains Mono',monospace;font-size:12.5px;font-weight:700;letter-spacing:.08em;color:var(--muted);text-transform:uppercase;}
.answer summary::-webkit-details-marker{display:none;}
.answer summary svg{width:15px;height:15px;fill:none;stroke:currentColor;stroke-width:2;stroke-linecap:round;stroke-linejoin:round;}
.answer summary .chev{margin-left:auto;transition:.2s;}
.answer[open] summary .chev{transform:rotate(180deg);}
.answer[open] summary{color:color-mix(in oklch,var(--accent) 60%,var(--ink));border-bottom:1px solid rgba(140,170,220,.14);}
.answer .abody{padding:14px 16px;font-size:14.5px;line-height:1.7;color:#cfe0f5;}
.answer .abody code,.answer .abody .mono{font-family:'JetBrains Mono',monospace;color:oklch(0.82 0.13 150);background:none;border:none;padding:0;}
.answer .abody .row{display:flex;gap:10px;flex-wrap:wrap;}
.answer .abody .row b{color:var(--muted);font-weight:600;min-width:74px;}

/* discussion box */
.discuss{margin-top:22px;padding:16px 18px;border-radius:14px;border:1px dashed rgba(140,170,220,.22);background:rgba(13,20,34,.4);}
.discuss .dh{display:flex;align-items:center;gap:9px;font-weight:800;font-size:14px;color:color-mix(in oklch,var(--accent) 60%,var(--ink));}
.discuss .dh svg{width:16px;height:16px;fill:none;stroke:var(--accent);stroke-width:2;stroke-linecap:round;stroke-linejoin:round;}
.discuss p{margin-top:8px;font-size:15px;line-height:1.6;color:#c7d4ea;}

/* ── Tabula recta (таблица Виженера) ──────────────────────────── */
.vig-wrap{margin-top:18px;overflow-x:auto;border-radius:14px;border:1px solid rgba(140,170,220,.16);
  background:#070b14;box-shadow:inset 0 0 0 1px rgba(0,0,0,.35);-webkit-overflow-scrolling:touch;}
.vig{border-collapse:separate;border-spacing:0;font-family:'JetBrains Mono',monospace;font-size:12.5px;margin:0 auto;}
.vig th,.vig td{width:27px;min-width:27px;height:27px;text-align:center;vertical-align:middle;
  border-right:1px solid rgba(140,170,220,.07);border-bottom:1px solid rgba(140,170,220,.07);color:#aebfda;}
.vig thead th{position:sticky;top:0;z-index:2;background:var(--accent);color:#06101c;font-weight:700;
  border-bottom:1px solid color-mix(in oklch,var(--accent) 60%,#000);}
.vig tbody th{position:sticky;left:0;z-index:1;background:var(--accent);color:#06101c;font-weight:700;
  border-right:1px solid color-mix(in oklch,var(--accent) 60%,#000);}
.vig thead th.corner{left:0;z-index:3;background:color-mix(in oklch,var(--accent) 60%,#06101c);color:var(--accent);}
.vig td{transition:background .08s;}
.vig td:hover{background:color-mix(in oklch,var(--accent) 32%,transparent);color:#fff;}
.vig-cap{margin-top:10px;font-size:13px;line-height:1.55;color:var(--muted);}
.vig-cap b{color:color-mix(in oklch,var(--accent) 65%,var(--ink));font-weight:700;}

/* pager */
.pager{display:grid;grid-template-columns:1fr 1fr;gap:16px;margin-top:50px;}
.pn{display:flex;flex-direction:column;gap:5px;padding:18px 20px;border-radius:16px;text-decoration:none;
  background:rgba(13,20,34,.6);border:1px solid rgba(140,170,220,.12);transition:.2s;min-height:70px;}
.pn:hover{border-color:var(--accent);transform:translateY(-3px);}
.pn-r{text-align:right;}
.pn-dir{font-family:'JetBrains Mono',monospace;font-size:12px;letter-spacing:.1em;color:var(--accent);}
.pn-ttl{font-weight:700;font-size:15px;color:var(--ink);}
.pn-off{visibility:hidden;}
@media(max-width:560px){.hero{flex-direction:column;text-align:center;align-items:center;}.practice{padding:24px 18px;}}

/* ════════════ LIGHT THEME (synced from roadmap) ════════════ */
html[data-theme="light"]{
  --n0:oklch(0.62 0.15 192);--n1:oklch(0.60 0.15 202);--n2:oklch(0.57 0.16 213);
  --n3:oklch(0.54 0.17 224);--n4:oklch(0.52 0.18 235);--n5:oklch(0.51 0.18 247);
  --n6:oklch(0.51 0.19 258);--n7:oklch(0.52 0.19 269);--n8:oklch(0.55 0.18 281);
  --bg:#eef2f9;--ink:#0d1726;--muted:#566782;
}
html[data-theme="light"] body::before{background-image:linear-gradient(rgba(40,70,130,.07) 1px,transparent 1px),linear-gradient(90deg,rgba(40,70,130,.07) 1px,transparent 1px);}
/* surfaces → light */
html[data-theme="light"] .back{background:#fff;border-color:rgba(40,70,120,.18);}
html[data-theme="light"] .emb{background:radial-gradient(120% 120% at 30% 20%,color-mix(in oklch,var(--accent) 14%,#fff),#fff);box-shadow:0 0 0 1px rgba(40,70,120,.08),0 14px 40px color-mix(in oklch,var(--accent) 18%,transparent);}
html[data-theme="light"] .theory .zone-tab{background:color-mix(in oklch,var(--accent) 8%,#fff);}
html[data-theme="light"] .def{background:#fff;}
html[data-theme="light"] .code{background:#f3f6fb;box-shadow:inset 0 0 0 1px rgba(40,70,120,.06);}
html[data-theme="light"] .code .code-bar{background:#e8eef7;border-bottom-color:rgba(40,70,120,.12);}
html[data-theme="light"] .code pre{color:#2c3a52;}
html[data-theme="light"] .code pre .g{color:oklch(0.52 0.15 150);}
html[data-theme="light"] .callout{background:color-mix(in oklch,var(--accent) 12%,#fff);}
html[data-theme="light"] .callout .ico{background:color-mix(in oklch,var(--accent) 18%,#fff);}
html[data-theme="light"] .practice{background:repeating-linear-gradient(0deg,transparent 0 33px,rgba(40,70,120,.05) 33px 34px),linear-gradient(180deg,#fff,#f4f7fc);box-shadow:0 24px 60px rgba(40,70,120,.12),0 0 0 1px rgba(40,70,120,.05) inset;}
html[data-theme="light"] .variant{background:#f6f9fd;border-color:rgba(40,70,120,.16);}
html[data-theme="light"] .variant .vh{background:color-mix(in oklch,var(--accent) 10%,#fff);border-bottom-color:rgba(40,70,120,.14);}
html[data-theme="light"] .steps li::before{background:color-mix(in oklch,var(--accent) 12%,#fff);}
html[data-theme="light"] .checks li::before{background:#fff;}
html[data-theme="light"] .practice code,html[data-theme="light"] .theory code,html[data-theme="light"] .lead code{background:#eaf0f8;border-color:rgba(40,70,120,.16);}
html[data-theme="light"] .answer{background:#f6f9fd;border-color:rgba(40,70,120,.18);}
html[data-theme="light"] .answer .abody{color:#2c3a52;}
html[data-theme="light"] .answer .abody code,html[data-theme="light"] .answer .abody .mono{color:oklch(0.5 0.15 150);}
html[data-theme="light"] .discuss{background:#f4f7fc;border-color:rgba(40,70,120,.22);}
html[data-theme="light"] .vig-wrap{background:#f3f6fb;box-shadow:inset 0 0 0 1px rgba(40,70,120,.06);}
html[data-theme="light"] .vig th,html[data-theme="light"] .vig td{color:#44546e;border-right-color:rgba(40,70,120,.1);border-bottom-color:rgba(40,70,120,.1);}
html[data-theme="light"] .pn{background:#fff;border-color:rgba(40,70,120,.14);}
/* body text → dark */
html[data-theme="light"] .theory p,html[data-theme="light"] .blist li,html[data-theme="light"] .variant ol li,html[data-theme="light"] .practice .pintro,html[data-theme="light"] .task-intro,html[data-theme="light"] .steps li,html[data-theme="light"] .checks li,html[data-theme="light"] .callout .ctxt,html[data-theme="light"] .discuss p{color:#3a4861;}
html[data-theme="light"] .theory p b,html[data-theme="light"] .theory li b,html[data-theme="light"] .steps li b,html[data-theme="light"] .checks li b,html[data-theme="light"] .variant ol li b{color:#0d1726;}
/* accent chips keep light text */
html[data-theme="light"] .practice .zone-tab{color:#fff;}
html[data-theme="light"] .practice .zone-tab svg{stroke:#fff;}
html[data-theme="light"] .vig thead th,html[data-theme="light"] .vig tbody th{color:#fff;}
html[data-theme="light"] .vig thead th.corner{background:var(--accent);color:#fff;}
html[data-theme="light"] .vig td:hover{color:#0d1726;}