:root{
  --paper:#F3F6F9; --card:#FFFFFF; --ink:#14213D; --ink2:#4A5670; --line:#D7DEE8; --line2:#EDF1F6;
  --blue:#1F5FD1; --blue-soft:#E3ECFF; --magenta:#D1286F; --green:#178F5B; --green-soft:#DFF4E9; --amber:#D98E00; --amber-soft:#FFF1D6; --red:#D23B3B; --red-soft:#FBE3E3;
  --m-bg:#DCE8FF; --m-fg:#1D4FAF; --n-bg:#FFE4CF; --n-fg:#A84E12; --s-bg:#E9E2FF; --s-fg:#5E3FB3; --g-bg:#DCF5EC; --g-fg:#176F55;
  --display:"Unbounded","Arial Black",Arial,sans-serif; --body:"Golos Text","Segoe UI",Roboto,Arial,sans-serif;
  --r:14px; --r-sm:8px;
}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}*{transition:none!important;animation:none!important}}
body{margin:0;background:var(--paper);color:var(--ink);font:16px/1.55 var(--body);
  background-image:linear-gradient(var(--line2) 1px,transparent 1px),linear-gradient(90deg,var(--line2) 1px,transparent 1px);background-size:28px 28px}
a{color:var(--blue)}
h1,h2,h3,h4{font-family:var(--display);font-weight:600;line-height:1.2;margin:0 0 .4em;letter-spacing:-.01em}
h1{font-size:30px}h2{font-size:22px}h3{font-size:17px}h4{font-size:15px}
p{margin:.4em 0 .8em}
.muted{color:var(--ink2)}
.wrap{max-width:1120px;margin:0 auto;padding:0 20px}
sub,sup{font-size:.72em}
button,input,select{font:inherit}
:focus-visible{outline:3px solid var(--magenta);outline-offset:2px}

/* шапка */
.top{background:var(--ink);color:#fff}
.top .wrap{display:flex;align-items:center;gap:18px;height:56px}
.top a{color:#fff;text-decoration:none}
.top .brand{font-family:var(--display);font-size:15px;letter-spacing:.02em}
.top .brand b{color:#FFC861}
.top nav{margin-left:auto;display:flex;gap:18px;font-size:14px}
.top nav a{opacity:.85}.top nav a:hover,.top nav a[aria-current]{opacity:1;text-decoration:underline;text-underline-offset:4px}

/* кнопки */
.btn{display:inline-flex;align-items:center;gap:8px;border:1.5px solid var(--line);background:var(--card);color:var(--ink);padding:10px 18px;border-radius:999px;cursor:pointer;text-decoration:none;font-weight:600;font-size:15px}
.btn:hover{border-color:var(--ink2)}
.btn.primary{background:var(--blue);border-color:var(--blue);color:#fff}.btn.primary:hover{background:#174AA8}
.btn.primary:disabled{background:#9DB2DC;border-color:#9DB2DC;cursor:default}
.btn.ghost{background:transparent}
.btn[hidden]{display:none}

/* плитки-элементы */
.tile,.mod-tile{--tile:var(--blue);position:relative;display:grid;align-content:start;background:var(--card);border:2px solid var(--tile);border-radius:var(--r);padding:14px 16px;color:var(--ink);text-decoration:none}
.tile-num{font-size:13px;color:var(--ink2);font-weight:600}
.tile-code{font-family:var(--display);font-size:46px;font-weight:700;color:var(--tile);line-height:1;margin:4px 0 8px}
.tile{width:112px;height:112px;padding:10px 12px}.tile .tile-code{font-size:40px;margin-top:2px}
.mod-tile{min-height:250px;transition:transform .15s}
.mod-tile:hover{transform:translateY(-3px);box-shadow:0 10px 28px rgba(20,33,61,.12)}
.mod-tile .tile-title{font-weight:700;font-size:17px;line-height:1.25}
.mod-tile .tile-sub{color:var(--ink2);font-size:13.5px;margin-top:4px;line-height:1.4}
.tile-prog{margin-top:auto;padding-top:12px;display:grid;gap:4px;font-size:12.5px;color:var(--ink2)}
.bar{display:block;height:7px;background:var(--line2);border-radius:4px;overflow:hidden}.bar-fill{display:block;height:100%;background:var(--tile)}
.mod-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(240px,1fr));gap:16px}

/* стартовая */
.hero{display:grid;grid-template-columns:1.05fr 1fr;gap:40px;align-items:center;padding:48px 0 28px}
.hero h1{font-size:40px;margin-bottom:14px}
.hero .lead{font-size:18px;color:var(--ink2);max-width:34em}
.hero-art{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}
.hero-art .tile{width:auto;height:auto;min-height:118px;padding:10px 12px}.hero-art .tile-title{font-size:12.5px;line-height:1.25;color:var(--ink2)}
.hero-art .tile-code{font-size:34px}
.how{display:grid;grid-template-columns:repeat(3,1fr);gap:16px;margin:22px 0 34px}
.how div{background:var(--card);border:1.5px solid var(--line);border-radius:var(--r);padding:14px 16px}
.how b{display:block;margin-bottom:4px}
.exam-cta{margin:32px 0 48px;background:var(--ink);color:#fff;border-radius:var(--r);padding:22px 24px;display:flex;gap:20px;align-items:center;flex-wrap:wrap}
.exam-cta p{margin:0;flex:1;min-width:240px}
.exam-cta .btn{background:#FFC861;border-color:#FFC861;color:var(--ink)}
#summary{margin:8px 0 18px}
footer{color:var(--ink2);font-size:13px;padding:24px 0 40px;border-top:1px solid var(--line);margin-top:20px}

/* модуль */
.mod-head{display:flex;gap:22px;align-items:center;padding:30px 0 16px}
.mod-head .lead{color:var(--ink2);margin:0;font-size:17px}
.tabs{display:flex;gap:6px;border-bottom:2px solid var(--line);margin-bottom:22px}
.tab{background:none;border:0;padding:10px 16px;font-weight:600;color:var(--ink2);cursor:pointer;border-bottom:3px solid transparent;margin-bottom:-2px;display:inline-flex;gap:8px;align-items:center}
.tab.on{color:var(--ink);border-bottom-color:var(--magenta)}
.badge{background:var(--line2);border-radius:999px;padding:1px 9px;font-size:12.5px;color:var(--ink2)}
.panel[hidden]{display:none}
.theory-grid{display:grid;grid-template-columns:240px 1fr;gap:28px;align-items:start}.theory-grid>*{min-width:0}.lessons{min-width:0}
.theory-aside{position:sticky;top:16px;background:var(--card);border:1.5px solid var(--line);border-radius:var(--r);padding:14px 16px}
.lesson-nav{list-style:none;margin:0;padding:0;counter-reset:l}
.lesson-nav li{counter-increment:l;padding:5px 0;font-size:14.5px;line-height:1.3}
.lesson-nav li::before{content:counter(l) '. ';color:var(--ink2)}
.lesson-nav li.done::before{content:'✓ ';color:var(--green);font-weight:700}
.lesson-nav a{color:var(--ink);text-decoration:none}.lesson-nav a:hover{text-decoration:underline}
.lesson{background:var(--card);border:1.5px solid var(--line);border-radius:var(--r);padding:22px 26px;margin-bottom:18px;scroll-margin-top:16px}
.prose{max-width:70ch}
.prose p,.prose li{font-size:16px}
.prose ul,.prose ol{padding-left:22px}
.prose .key{background:var(--blue-soft);border-left:4px solid var(--blue);padding:10px 14px;border-radius:0 var(--r-sm) var(--r-sm) 0;margin:12px 0}
.prose .ex{background:var(--line2);padding:10px 14px;border-radius:var(--r-sm);margin:12px 0}
.prose .ex b:first-child{color:var(--magenta)}
.prose .warn{background:var(--amber-soft);border-left:4px solid var(--amber);padding:10px 14px;border-radius:0 var(--r-sm) var(--r-sm) 0;margin:12px 0}
.prose table,.tbl{border-collapse:collapse;width:100%;margin:10px 0;font-size:15px}
.prose th,.prose td,.tbl td,.tbl th{border:1px solid var(--line);padding:6px 10px;text-align:left;vertical-align:top}
.prose th{background:var(--line2)}
.prose .f{font-weight:600;white-space:nowrap}
.done-check{display:inline-flex;gap:8px;align-items:center;margin-top:12px;color:var(--ink2);font-size:14.5px;cursor:pointer}
.theory-end{text-align:center;padding:16px 0 30px}
.widget{margin-top:16px;border-top:1px dashed var(--line);padding-top:16px}
.field{display:flex;gap:8px;align-items:center;flex-wrap:wrap;margin:6px 0;font-size:15px}
.field.wide{width:100%}
.inp{border:1.5px solid var(--line);border-radius:var(--r-sm);padding:8px 12px;background:#fff;min-width:0}
.inp:focus{border-color:var(--blue)}
.inp.big{font-size:20px;padding:10px 14px;width:min(100%,320px)}
.inp.sm{width:80px}
.inp.coef{width:58px;text-align:center;font-size:18px;padding:6px}
.err{color:var(--red)}

/* периодическая таблица */
.ptable-wrap{overflow-x:auto;padding-bottom:6px}
.ptable{display:grid;grid-template-columns:repeat(18,minmax(44px,1fr));grid-template-rows:18px;grid-auto-rows:54px;gap:3px;min-width:860px;position:relative}
.pgroup{font-size:11px;color:var(--ink2);text-align:center;align-self:end;line-height:1}
.pcell{border:0;border-radius:6px;padding:3px 4px;display:grid;grid-template-columns:1fr;text-align:left;cursor:pointer;line-height:1.05;transition:transform .1s}
.pcell:hover{transform:scale(1.08);z-index:1}
.pcell.sel{outline:3px solid var(--magenta)}
.pz{font-size:9.5px;opacity:.7}.psym{font-family:var(--display);font-weight:700;font-size:15px}.pname{font-size:8.5px;opacity:.8;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.t-m{background:var(--m-bg);color:var(--m-fg)}.t-n{background:var(--n-bg);color:var(--n-fg)}.t-s{background:var(--s-bg);color:var(--s-fg)}.t-g{background:var(--g-bg);color:var(--g-fg)}
.plegend{display:flex;gap:8px;flex-wrap:wrap;margin:8px 0;font-size:12.5px}.plegend span{padding:2px 10px;border-radius:999px}
.ptable-info{margin-top:10px}
.el-card{display:grid;grid-template-columns:auto minmax(0,1fr);gap:4px 18px;align-items:start;background:var(--line2);border-radius:var(--r);padding:14px 18px;max-width:560px}
.el-card-head{grid-column:1/-1;display:flex;gap:12px;align-items:baseline}
.el-card-head .el-sym{font-family:var(--display);font-size:34px;font-weight:700;padding:0 10px;border-radius:8px}
.el-card h4,.el-card .muted{grid-column:1/-1;margin:0}
.el-card>*{min-width:0}.el-facts{margin:0;min-width:0;display:grid;grid-template-columns:auto minmax(0,1fr);gap:3px 10px;font-size:14px}.el-facts dt{color:var(--ink2)}.el-facts dd{margin:0}
.atom-svg .nucleus{fill:var(--magenta)}.atom-svg .orbit{fill:none;stroke:var(--ink2);stroke-width:1;stroke-dasharray:3 3}.atom-svg .electron{fill:var(--blue)}.atom-svg .orbit-label{font-size:11px;fill:var(--ink2)}
.molar-out{margin-top:8px}

/* тренажёр */
.train-head{display:flex;justify-content:space-between;gap:14px;align-items:center;flex-wrap:wrap}
.toolbar{display:flex;gap:8px}
.task-map{display:flex;flex-wrap:wrap;gap:6px;margin:10px 0 18px}
.tnum{width:36px;height:36px;border-radius:8px;border:1.5px solid var(--line);background:var(--card);cursor:pointer;font-weight:600;color:var(--ink2)}
.tnum.ok{background:var(--green-soft);border-color:var(--green);color:var(--green)}
.tnum.fail{background:var(--red-soft);border-color:var(--red);color:var(--red)}
.tnum.cur{outline:3px solid var(--magenta);outline-offset:1px}
.task-stage{max-width:820px}
.task-card{background:var(--card);border:1.5px solid var(--line);border-radius:var(--r);padding:22px 26px}
.task-top{display:flex;justify-content:space-between;font-size:13px;color:var(--ink2);margin-bottom:10px}
.task-q{font-size:18px;margin-bottom:14px}
.task-actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:16px}
.feedback{margin-top:14px;padding:12px 16px;border-radius:var(--r-sm);display:none}
.feedback.ok{display:block;background:var(--green-soft);color:#0F5E3B}
.feedback.bad{display:block;background:var(--red-soft);color:#8E1F1F}
.feedback.warn{display:block;background:var(--amber-soft);color:#6B4700}
.feedback.info{display:block;background:var(--blue-soft);color:var(--ink)}
.feedback p{margin:6px 0 0}
.opts{display:grid;gap:8px}
.opt{display:flex;gap:12px;align-items:flex-start;border:1.5px solid var(--line);border-radius:var(--r-sm);padding:10px 14px;cursor:pointer;font-size:17px}
.opt:hover{border-color:var(--blue)}.opt input{margin-top:5px;accent-color:var(--blue)}
.input-row{display:flex;gap:10px;align-items:center}
.unit{color:var(--ink2)}
.atom-form{display:flex;gap:16px;flex-wrap:wrap}
.eq{display:flex;align-items:center;gap:8px;flex-wrap:wrap;font-size:22px}
.eq-term{display:inline-flex;align-items:center;gap:4px}.eq-sign{color:var(--ink2);padding:0 2px}
.cls-row{display:flex;gap:14px;align-items:center;padding:8px 0;border-bottom:1px solid var(--line2);flex-wrap:wrap}
.cls-item{font-size:19px;font-weight:600;min-width:250px}
.chips{display:flex;gap:6px;flex-wrap:wrap}
.chip{border:1.5px solid var(--line);background:#fff;border-radius:999px;padding:5px 12px;cursor:pointer;font-size:14.5px}
.chip.on{background:var(--blue);border-color:var(--blue);color:#fff}
.match-row{display:grid;grid-template-columns:minmax(120px,1fr) 2fr;gap:12px;align-items:center;padding:6px 0}
.match-l{font-size:18px;font-weight:600}
.exam-prog{font-weight:600;color:var(--ink2);margin:14px 0}
.result h2{font-size:28px}
.result-list{list-style:none;padding:0}.result-list li{padding:5px 0;border-bottom:1px solid var(--line2)}.result-list li.good::before{content:'✓ ';color:var(--green)}
.result-list li:not(.good)::before{content:'• ';color:var(--red)}

@media (max-width:860px){
  .hero{grid-template-columns:1fr;gap:22px;padding-top:28px}.hero h1{font-size:30px}
  .how{grid-template-columns:1fr}
  .theory-grid{grid-template-columns:1fr}.theory-aside{position:static}
  .mod-head{flex-direction:column;align-items:flex-start;gap:12px}
  .lesson{padding:16px}.task-card{padding:16px}
  .top nav{gap:12px;font-size:13px}
}
@media (max-width:640px){.el-card{grid-template-columns:1fr}.el-card .atom-svg{max-width:100%;height:auto}.atom-form .field{width:100%}.el-card-head{flex-wrap:wrap}}

/* иллюстрации к заданиям */
.brand-sub{display:block;font-family:var(--body);font-size:11.5px;opacity:.8;font-weight:400;letter-spacing:0;margin-top:1px}
.top .wrap{height:auto;min-height:56px;padding-top:8px;padding-bottom:8px}
.lead-sub{font-size:20px;color:var(--magenta);font-weight:600;margin:-8px 0 14px}
.vis{background:var(--line2);border-radius:var(--r-sm);padding:12px 14px;margin:0 0 14px}
.vis-svg{display:block;max-width:100%;height:auto}
.vis-row{display:flex;gap:14px;flex-wrap:wrap;align-items:flex-start}
.vis-item{background:#fff;border:1px solid var(--line);border-radius:var(--r-sm);padding:8px 10px;text-align:center;font-size:13px}
.vis-item.clickable{cursor:pointer}.vis-item.clickable:hover,.vis-item.on{border-color:var(--magenta)}
.vis-lbl{font-size:13px;color:var(--ink2);margin-top:4px;line-height:1.35}
.vis-cap{font-size:13.5px;color:var(--ink2);margin:8px 0 0}
.vis-ctl{display:flex;gap:6px;flex-wrap:wrap;margin-top:8px}
.vis-range{width:220px;accent-color:var(--blue)}
.mole-card{display:grid;gap:3px;font-size:14px;padding:8px 12px;background:#fff;border:1px solid var(--line);border-radius:var(--r-sm)}
.mole-card b{font-size:16px;color:var(--navy)}
.ptable.compact{grid-template-columns:repeat(18,minmax(28px,1fr));grid-auto-rows:30px;min-width:560px;gap:2px}
.ptable.compact .pcell{padding:2px;border-radius:4px}.ptable.compact .psym{font-size:11px}
.pcell.hl{outline:3px solid var(--magenta);outline-offset:-1px;z-index:1}
.gas-p{animation:gasmove 2.4s ease-in-out infinite alternate}
@keyframes gasmove{from{transform:translate(0,0)}to{transform:translate(9px,-7px)}}
.diff-p{animation:diffmove 4s ease-in-out infinite alternate}
@keyframes diffmove{to{transform:translate(var(--dx),0)}}
.ox-row{display:flex;gap:14px;flex-wrap:wrap;align-items:flex-end}
.ox-atom{display:grid;justify-items:center;background:#fff;border:1px solid var(--line);border-radius:var(--r-sm);padding:6px 12px;min-width:84px}
.ox-atom.unk{border-color:var(--magenta);background:#FFF0F6}
.ox-st{font-size:13px;color:var(--magenta);font-weight:700}.ox-sym{font-size:24px;font-weight:700;color:var(--navy)}.ox-part{font-size:12px;color:var(--ink2)}
.bal-tbl{width:auto;min-width:260px;font-size:14px}.bal-tbl td,.bal-tbl th{padding:4px 12px}.okm{color:var(--green);font-weight:700}.badm{color:var(--red);font-weight:700}
.stoich{display:flex;gap:8px;align-items:center;flex-wrap:wrap}
.st-col{background:#fff;border:1px solid var(--line);border-radius:var(--r-sm);padding:8px 12px;text-align:center}.st-col.given{border-color:var(--magenta);background:#FFF0F6}
.st-f{font-size:19px;font-weight:700;color:var(--navy)}.st-n{font-size:13px;color:var(--ink2)}.st-sign{font-size:20px;color:var(--ink2)}
.redox{display:flex;gap:12px;align-items:center;flex-wrap:wrap;font-size:22px;font-weight:700;color:var(--navy)}
.rx-arrow{color:var(--magenta);font-size:16px;font-weight:600}
.big-sym{font-size:30px;font-weight:700;color:var(--navy);line-height:1.1}
.cls-card{--c:var(--blue);border-top:4px solid var(--c);min-width:120px}.cls-card b{display:block;color:var(--c);font-size:16px}.cls-pat{display:block;font-weight:600;margin:2px 0}
.gen-row{display:flex;gap:8px;align-items:center;flex-wrap:wrap;margin:6px 0}
.gen-node{background:#fff;border:1px solid var(--line);border-radius:999px;padding:5px 14px;font-weight:600}.gen-arr{color:var(--magenta)}
@media (max-width:640px){.brand-sub{display:none}.vis-range{width:160px}}

/* иллюстрации в теории */
.prose .vis{margin:14px 0;max-width:none}
.prose .vis table{width:auto;margin:6px 0}
.prose .vis p{font-size:13.5px}
.prose .vis .vis-lbl{font-size:13px}
.theory-vis .equation{display:flex;flex-wrap:wrap;gap:6px;align-items:center;font-size:20px;font-weight:700;color:var(--navy)}
.theory-vis .equation .coef{width:46px;font-size:18px;padding:3px 4px;text-align:center;border:1.5px solid var(--line);border-radius:6px;font-weight:700}
.theory-vis .equation .term{display:inline-flex;align-items:center;gap:3px}.theory-vis .equation .sign{color:var(--ink2);font-weight:500;margin:0 4px}
.eb-row{display:flex;gap:12px;align-items:center;flex-wrap:wrap;background:#fff;border:1px solid var(--line);border-radius:var(--r-sm);padding:6px 12px;margin:6px 0;font-size:16px}
.eb-n{font-size:22px;font-weight:700;color:var(--magenta);min-width:26px;text-align:center}.eb-row .rx{font-weight:700;color:var(--navy)}.eb-e{color:var(--ink2);font-size:14px}
.salt-out{background:#fff;border:1px solid var(--line);border-radius:var(--r-sm);padding:10px 14px;margin-top:10px}
.salt-f{font-size:30px;font-weight:700;color:var(--navy);line-height:1.1}.salt-name{font-size:17px;font-weight:600;color:var(--magenta);margin:2px 0 4px}
.rm-tbl{font-size:13px;border-collapse:collapse;min-width:520px}.rm-tbl th{font-weight:600;padding:4px 6px;text-align:center;font-size:12px}.rm-tbl th:first-child{text-align:left}.rm-tbl td{padding:3px;text-align:center}
.rm-cell{width:38px;height:30px;border-radius:6px;border:1px solid var(--line);background:#fff;cursor:pointer;font-weight:700}
.rm-cell.yes{color:var(--green)}.rm-cell.no{color:#9AA5B1}.rm-cell.on{outline:2px solid var(--magenta)}.rm-cell:hover{border-color:var(--magenta)}
.ie-step{background:#fff;border:1px solid var(--line);border-radius:var(--r-sm);padding:8px 12px;margin:6px 0}
.ie-title{font-size:13px;color:var(--ink2)}.ie-eq{font-size:18px;font-weight:700;color:var(--navy);margin-top:3px}
.spect{color:#9AA5B1;text-decoration:line-through;font-weight:500}
@media (max-width:640px){.theory-vis .equation{font-size:17px}.salt-f{font-size:24px}}
.tbl-scroll{overflow-x:auto;margin:10px 0}.tbl-scroll table{margin:0;min-width:360px}