/* CKC111 Discrete Structures: study site styles
   Shared design tokens and components for Weeks 1 to 3. */

/* CKC111 Week 3: Basic Algorithms - styles */

:root{
  --bg:#F6F5FA; --surface:#FFFFFF; --ink:#1B1830; --muted:#5E5A74; --line:#DAD6E6;
  --brand:#6B2FA0; --brand-ink:#FFFFFF; --soft:#EFE9F8;
  --t:#0A6C74; --t-bg:#DDF1F1; --f:#B8431A; --f-bg:#FBE6DC; --focus:#DB5A1F;
  --head:"Bricolage Grotesque","Segoe UI",system-ui,sans-serif;
  --body:"Literata",Georgia,"Times New Roman",serif;
  --sym:"Noto Sans Math","Cambria Math","STIX Two Math","Segoe UI Symbol",serif;
  --mono:ui-monospace,"SF Mono","Cascadia Code",Menlo,Consolas,monospace;
  box-sizing:border-box;
  padding-top:env(safe-area-inset-top,0px);
  padding-bottom:env(safe-area-inset-bottom,0px);
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --bg:#16131F; --surface:#201C2D; --ink:#EEEAF8; --muted:#A9A3C0; --line:#3A3550;
    --brand:#B58CE8; --brand-ink:#16131F; --soft:#2B2540;
    --t:#6FD3D6; --t-bg:#12363A; --f:#FF9A70; --f-bg:#43231A;
  }
}
:root[data-theme="dark"]{
  --bg:#16131F; --surface:#201C2D; --ink:#EEEAF8; --muted:#A9A3C0; --line:#3A3550;
  --brand:#B58CE8; --brand-ink:#16131F; --soft:#2B2540;
  --t:#6FD3D6; --t-bg:#12363A; --f:#FF9A70; --f-bg:#43231A;
}

html{scroll-padding-top:calc(env(safe-area-inset-top,0px) + 70px);scroll-behavior:smooth}
*,*::before,*::after{box-sizing:inherit}
body{margin:0;background:var(--bg);color:var(--ink);font-family:var(--body);font-size:1.05rem;line-height:1.7}
a{color:var(--brand)}
:focus-visible{outline:3px solid var(--focus);outline-offset:2px;border-radius:4px}
.sym,.e{font-family:var(--sym)}
h1,h2,h3{font-family:var(--head);line-height:1.15;margin:0 0 .6em;letter-spacing:-.01em}
h2{font-size:clamp(1.6rem,3vw,2.1rem);margin-top:0}
h3{font-size:1.2rem;margin-top:1.8em}
p{margin:0 0 1em;max-width:66ch}
ul,ol{max-width:66ch;padding-left:1.3em}
li{margin-bottom:.35em}
sub{font-size:.7em}

/* ---------- layout ---------- */
.prog{margin-top:1.2rem;font-size:.85rem;color:var(--muted)}
.bar{height:6px;background:var(--line);border-radius:3px;margin-top:6px;overflow:hidden}
.bar i{display:block;height:100%;width:0;background:var(--brand);transition:width .3s}

main{padding:0 clamp(18px,4vw,56px) 80px;min-width:0}
section{padding:56px 0 8px;border-bottom:1px solid var(--line)}
section:last-of-type{border-bottom:0}
.hero{padding-top:44px}
.hero h1{font-size:clamp(2rem,5vw,3.3rem);max-width:18ch}
.hero .lead{font-size:1.15rem;color:var(--muted);max-width:58ch}

/* ---------- components ---------- */
.card{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:20px 22px;margin:20px 0}
.beyond{font-size:.92rem;color:var(--muted);border-left:3px solid var(--line);padding:2px 0 2px 12px;margin:1em 0;max-width:66ch}
.trap{background:var(--f-bg);border-left:4px solid var(--f);padding:12px 16px;border-radius:0 8px 8px 0;max-width:66ch;margin:1.2em 0}
.trap b{color:var(--f)}
.tip{background:var(--t-bg);border-left:4px solid var(--t);padding:12px 16px;border-radius:0 8px 8px 0;max-width:66ch;margin:1.2em 0}
.tip b{color:var(--t)}
.idea{background:var(--soft);border-left:4px solid var(--brand);padding:12px 16px;border-radius:0 8px 8px 0;max-width:66ch;margin:1.2em 0}

table{border-collapse:collapse;font-family:var(--sym);font-size:1rem;margin:12px 0}
th,td{border:1px solid var(--line);padding:6px 14px;text-align:center}
th{background:var(--soft);font-weight:600}
td.l{text-align:left;font-family:var(--body)}
th.l{text-align:left;font-family:var(--head)}
td.num{font-family:var(--mono)}
.scroll{overflow-x:auto;max-width:100%}

pre.code{font-family:var(--mono);font-size:.92rem;line-height:1.55;background:var(--surface);border:1px solid var(--line);border-radius:10px;padding:14px 16px;overflow-x:auto;margin:12px 0;max-width:100%;white-space:pre}
pre.code b{color:var(--brand);font-weight:700}

.btn,.keys button{font-family:var(--head);font-size:.95rem;padding:8px 14px;border-radius:8px;border:1.5px solid var(--line);background:var(--surface);color:var(--ink);cursor:pointer}
.btn.primary{background:var(--brand);color:var(--brand-ink);border-color:var(--brand)}
.btn:disabled{opacity:.45;cursor:not-allowed}
.btn:hover:not(:disabled){border-color:var(--brand)}
.togrow{display:flex;gap:8px;flex-wrap:wrap;margin:10px 0}
.small{font-size:.88rem;color:var(--muted)}
.err{color:var(--f);font-family:var(--head);margin:8px 0}
select{font:inherit;font-family:var(--head);font-size:.92rem;padding:6px 8px;border-radius:8px;border:1.5px solid var(--line);background:var(--surface);color:var(--ink)}
input[type=text]{font-family:var(--mono);font-size:1rem;padding:8px 10px;border-radius:8px;border:1.5px solid var(--line);background:var(--bg);color:var(--ink);min-width:0}
.v-T{color:var(--t);background:var(--t-bg);font-weight:700}
.v-F{color:var(--f);background:var(--f-bg);font-weight:700}

/* ---------- the step player ---------- */
.player{background:var(--surface);border:1px solid var(--line);border-radius:14px;padding:16px;margin:18px 0}
.pl-in{display:flex;gap:8px;flex-wrap:wrap;align-items:center}
.pl-in label{font-family:var(--head);font-size:.9rem}
.pl-in input.list{flex:1 1 220px}
.pl-in input.xin{width:6ch}
.pl-err{min-height:1.2em;color:var(--f);font-family:var(--head);font-size:.9rem;margin:6px 0 0}
.pl-ctl{display:flex;gap:8px;flex-wrap:wrap;align-items:center;margin:10px 0}
.pl-count{font-family:var(--head);font-size:.9rem;color:var(--muted);margin-left:4px}
.pl-body{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1.1fr);gap:16px}
.pl-code{font-family:var(--mono);font-size:.88rem;line-height:1.6;background:var(--bg);border:1px solid var(--line);border-radius:10px;padding:10px 0;overflow-x:auto}
.pl-code div{padding:1px 12px 1px calc(12px + var(--ind,0) * 1.4em);white-space:nowrap;border-left:4px solid transparent}
.pl-code div.on{background:var(--soft);border-left-color:var(--brand)}
.pl-code b{color:var(--brand)}
.cells{display:flex;flex-wrap:wrap;gap:6px;margin-bottom:10px}
.cell{display:flex;flex-direction:column;align-items:center;min-width:46px}
.cell .box{width:100%;text-align:center;font-family:var(--mono);font-size:1.05rem;padding:8px 6px;border:2px solid var(--line);border-radius:8px;background:var(--bg)}
.cell .ix{font-size:.75rem;color:var(--muted);font-family:var(--head);margin-top:2px}
.cell .tag{font-size:.72rem;font-family:var(--head);min-height:1.1em;color:var(--muted)}
.cell.active .box{border-color:var(--focus);background:var(--f-bg)}
.cell.best .box,.cell.sorted .box{border-color:var(--t);background:var(--t-bg)}
.cell.mid .box{border-color:var(--brand);background:var(--soft);font-weight:700}
.cell.found .box{border-color:var(--t);background:var(--t-bg);font-weight:700;box-shadow:0 0 0 2px var(--t)}
.cell.dim{opacity:.35}
.vars{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:8px;min-height:2em}
.vars span{font-family:var(--mono);font-size:.9rem;background:var(--soft);border-radius:999px;padding:2px 10px}
.note{margin:0;min-height:3.4em;max-width:none;font-size:1rem}

/* ---------- greedy lab ---------- */
.lab label{font-family:var(--head);font-size:.9rem;display:block;margin:10px 0 4px}
.lab input[type=text]{width:100%;max-width:420px}
.verdict-box{font-family:var(--head);font-weight:700;padding:10px 14px;border-radius:8px;margin:10px 0;display:inline-block;max-width:100%}

/* ---------- detective, recall, practice ---------- */
.det{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:16px 18px;margin:14px 0}
.det .row,.q .row{display:flex;gap:8px;flex-wrap:wrap;margin-top:10px;align-items:center}
.fb{margin-top:10px;padding:10px 14px;border-radius:8px;max-width:none}
.fb.ok{background:var(--t-bg);border-left:4px solid var(--t)}
.fb.ask{background:var(--soft);border-left:4px solid var(--brand)}

.q{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:18px 20px;margin:16px 0}
.q .top{display:flex;gap:10px;align-items:center;margin-bottom:6px;font-family:var(--head)}
.lvl{font-size:.85rem;padding:2px 10px;border-radius:999px;background:var(--soft);color:var(--brand);font-weight:600}
.q .txt{max-width:none;margin-bottom:10px}
.q textarea{width:100%;min-height:90px;font-family:var(--mono);font-size:.95rem;padding:10px 12px;border-radius:8px;border:1.5px solid var(--line);background:var(--bg);color:var(--ink);resize:vertical}
.hint,.sol{margin-top:10px;padding:10px 14px;border-radius:8px;max-width:none}
.hint{background:var(--soft)}
.sol{background:var(--t-bg);border-left:4px solid var(--t)}
.sol pre{font-family:var(--mono);font-size:.88rem;margin:6px 0;white-space:pre-wrap}
.objs{display:grid;gap:10px;margin:12px 0}
.objs .o{display:grid;grid-template-columns:1fr auto;gap:12px;align-items:center}
#cp-out{margin-top:14px}

/* ---------- small screens ---------- */
@media (max-width:860px){
  html{scroll-padding-top:calc(env(safe-area-inset-top,0px) + 64px)}
  .pl-body{grid-template-columns:1fr}
}
@media (prefers-reduced-motion:reduce){html{scroll-behavior:auto}.bar i{transition:none}}

/* ---------- components used only by Week 1 ---------- */
.sym{font-family:var(--sym)}
code,.mono{font-family:var(--sym)}
.promise{display:grid;grid-template-columns:1fr auto;gap:22px;align-items:center}
.promise .big{font-family:var(--sym);font-size:clamp(2.6rem,7vw,4.4rem);line-height:1;text-align:center;min-width:5.5ch}
.promise .res{font-family:var(--head);font-weight:700;font-size:1.1rem;margin-top:.25rem;text-align:center}
.tog{font:inherit;font-family:var(--head);font-size:.98rem;padding:9px 14px;border-radius:999px;border:1.5px solid var(--line);background:var(--surface);color:var(--ink);cursor:pointer;display:inline-flex;gap:8px;align-items:center}
.tog b{font-family:var(--sym);min-width:1.1em;text-align:center}
.tog[aria-pressed="true"]{border-color:var(--t);background:var(--t-bg);color:var(--t)}
.tog[aria-pressed="false"]{border-color:var(--f);background:var(--f-bg);color:var(--f)}
.msg{min-height:3.2em;margin:.4rem 0 0;max-width:none}
tr.hit td{outline:2px solid var(--brand);outline-offset:-2px}
th.final,td.final{border-left:3px solid var(--brand)}
tr.diff td{box-shadow:inset 0 0 0 2px var(--focus)}
.tabs{display:flex;gap:6px;flex-wrap:wrap;margin-bottom:6px}
.tab{font-family:var(--sym);font-size:1.1rem;padding:6px 14px;border:1.5px solid var(--line);background:var(--surface);color:var(--ink);border-radius:8px;cursor:pointer}
.tab[aria-selected="true"]{background:var(--brand);color:var(--brand-ink);border-color:var(--brand)}
.sorter{display:grid;gap:8px;margin:12px 0}
.sorter button{text-align:left;font:inherit;background:var(--surface);color:var(--ink);border:1.5px solid var(--line);border-radius:10px;padding:10px 14px;cursor:pointer}
.sorter button .verdict{display:block;font-family:var(--head);font-size:.92rem;margin-top:4px}
.sorter button.yes{border-color:var(--t)}
.sorter button.yes .verdict{color:var(--t)}
.sorter button.no{border-color:var(--f)}
.sorter button.no .verdict{color:var(--f)}
.keys{display:flex;gap:6px;flex-wrap:wrap;margin:8px 0}
.parsed{font-family:var(--sym);color:var(--muted);font-size:.95rem;margin:6px 0}
ol.proof{list-style:none;padding:0;margin:12px 0;counter-reset:s;max-width:none}
ol.proof li{counter-increment:s;display:grid;grid-template-columns:2rem 1fr auto;gap:10px;align-items:baseline;padding:8px 0;border-bottom:1px dashed var(--line);margin:0}
ol.proof li::before{content:counter(s);font-family:var(--head);color:var(--muted)}
ol.proof .e{font-family:var(--sym);font-size:1.05rem}
ol.proof .why{font-size:.9rem;color:var(--muted);text-align:right}
details{max-width:none;margin:14px 0}
summary{cursor:pointer;font-family:var(--head);font-weight:600}
.q .row{display:flex;gap:8px;flex-wrap:wrap;margin-top:10px;align-items:center}
.sol .e{font-family:var(--sym)}

/* ---------- site chrome: week switcher ---------- */
.week[hidden],.navgroup[hidden]{display:none}
[id$="-cp-out"]{margin-top:14px}
.w1 .lab input[type=text]{font-family:var(--sym);font-size:1.15rem;width:100%;max-width:none}
.w1 .q textarea{font-family:var(--sym);font-size:1rem}
.pending{background:var(--surface);border:1px dashed var(--brand);border-radius:12px;padding:20px 22px;margin:20px 0}
.pending ul{margin-bottom:.5em}

/* mobile additions for week 1 pieces and the week switcher */
@media (max-width:860px){
  .navgroup{display:contents}
  .navgroup[hidden]{display:none}
  .promise{grid-template-columns:1fr}
  ol.proof li{grid-template-columns:1.6rem 1fr}
  ol.proof .why{grid-column:2;text-align:left}
}

/* ---------- Weeks 4 and 5: relations ---------- */
.explorer .ex-body{display:grid;grid-template-columns:auto minmax(0,1fr);gap:22px;align-items:start}
.egrid{border-collapse:separate;border-spacing:3px;font-family:var(--head);margin:6px 0}
.egrid th{background:none;border:0;padding:4px 8px;font-weight:600;color:var(--muted)}
.egrid td{border:0;padding:0}
.gcell{width:42px;height:42px;border:2px solid var(--line);background:var(--bg);color:var(--brand);border-radius:8px;font-size:1.25rem;line-height:1;cursor:pointer;font-family:var(--sym)}
.egrid td.diag .gcell{background:var(--t-bg);border-color:var(--t)}
.gcell[aria-pressed="true"]{background:var(--brand);border-color:var(--brand);color:var(--brand-ink)}
.gcell:hover{border-color:var(--brand)}
.mono-pairs{font-family:var(--sym)}
.prow{display:grid;grid-template-columns:7.5rem 3.4rem minmax(0,1fr);gap:8px;align-items:baseline;padding:6px 0;border-bottom:1px dashed var(--line)}
.pname{font-family:var(--head);font-weight:600}
.ptag{font-family:var(--head);font-size:.82rem;text-align:center;border-radius:999px;padding:1px 8px}
.pwhy{font-size:.95rem;font-family:var(--sym)}
.calc div{padding:4px 0;font-family:var(--sym);overflow-wrap:anywhere}
table.mx td{min-width:2.2rem}
table.mx td.one{font-weight:700;background:var(--t-bg);color:var(--t)}
table.mx td.zero{color:var(--muted)}
.dg{width:100%;max-width:340px;height:auto;display:block}
.dg-edge{fill:none;stroke:var(--muted);stroke-width:1.6}
.dg-arrow{fill:var(--muted)}
.dg-node{fill:var(--soft);stroke:var(--brand);stroke-width:2}
.dg-label{fill:var(--ink);font-family:var(--sym);font-size:14px}
.tv-body{display:grid;grid-template-columns:minmax(0,1fr) minmax(0,1fr);gap:20px;margin-top:10px}
.tv-h{font-size:1rem;margin:14px 0 6px}
.mxarea{width:100%;max-width:420px;font-family:var(--mono);font-size:1rem;padding:8px 10px;border:1.5px solid var(--line);border-radius:8px;background:var(--bg);color:var(--ink)}
@media (max-width:860px){
  .explorer .ex-body,.tv-body{grid-template-columns:1fr}
  .prow{grid-template-columns:6.2rem 3rem minmax(0,1fr)}
}

/* ---------- Exam Lab ---------- */
.xlab .xctl{display:flex;gap:12px;flex-wrap:wrap;align-items:flex-end;margin-bottom:10px}
.xlab .xctl label,.xfield label{font-family:var(--head);font-size:.9rem;display:block;margin:0 0 4px}
.xlab select{min-width:12rem;max-width:100%}
.xlab .xcode-row input{width:16rem;max-width:100%}
.xq{border-top:1px solid var(--line);padding-top:14px;margin-top:10px}
#w6-mock-box .xq{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:16px 18px;margin:14px 0}
.xq .top{display:flex;gap:10px;align-items:center;flex-wrap:wrap;margin-bottom:6px;font-family:var(--head)}
.xcode{margin-left:auto;font-family:var(--mono)}
.xprompt{max-width:none;margin-bottom:10px;overflow-wrap:anywhere}
.xprompt pre.code{margin:8px 0}
.xfield{margin:10px 0}
.xfield input[type=text]{width:100%;max-width:520px}
.xchoices{display:grid;gap:6px}
.xopt{display:flex;gap:8px;align-items:flex-start;font-family:var(--body);font-size:1rem;margin:0;cursor:pointer}
.xopt input{margin-top:.35em}
.xgrid input{width:4.2ch;text-align:center;font-family:var(--mono)}
.xgrid th{font-weight:600}
.xtimer{font-family:var(--head);margin:10px 0}
.xbar{display:grid;grid-template-columns:7rem minmax(0,1fr) 8rem;gap:10px;align-items:center;margin:6px 0}
.xbar .bar{margin:0}
.props-sol{margin-top:8px}
.dg-w{fill:var(--ink);font-family:var(--mono);font-size:11px}
.dg-wbg{fill:var(--surface);stroke:var(--line);stroke-width:1}
details{border:1px solid var(--line);border-radius:10px;padding:8px 14px;margin:8px 0;background:var(--surface)}
details[open]{padding-bottom:12px}
details summary{padding:4px 0}
@media (max-width:860px){.xbar{grid-template-columns:5.5rem minmax(0,1fr)}.xbar .small{grid-column:1 / -1}.xcode{margin-left:0}}
.dg-arrowhead{fill:var(--muted);stroke:none}
.skip{position:absolute;left:-999px;top:8px;z-index:100;background:var(--brand);color:var(--brand-ink);padding:10px 14px;border-radius:8px;font-family:var(--head)}
.skip:focus{left:8px}

/* =====================================================
   SITE CHROME (v2): top tab bar, section rail, mobile sheet, home
   ===================================================== */
:root{--topbar-h:74px;padding-top:0;padding-bottom:0}
html{scroll-padding-top:calc(var(--topbar-h) + 16px)}

.topbar{position:sticky;top:0;z-index:40;background:var(--surface);border-bottom:1px solid var(--line);padding-top:env(safe-area-inset-top,0px)}
.topbar-in{max-width:1280px;margin:0 auto;display:flex;align-items:center;gap:14px;padding:0 20px;min-height:var(--topbar-h)}
.brandlink{display:flex;align-items:center;gap:10px;text-decoration:none;color:var(--ink);font-family:var(--head);flex:0 0 auto;border-radius:10px}
.brandlink .mark{width:36px;height:36px;border-radius:10px;background:var(--brand);color:var(--brand-ink);display:grid;place-items:center;font-family:var(--sym);font-size:1.2rem;font-weight:700}
.brandlink .bt{display:flex;flex-direction:column;line-height:1.15}
.brandlink .bt b{font-size:1.02rem}
.brandlink .bt span{font-size:.72rem;color:var(--muted)}
.wtabs{display:flex;gap:4px;flex:1 1 auto;min-width:0;overflow-x:auto;scrollbar-width:none;scroll-snap-type:x proximity;padding:8px 2px}
.wtabs::-webkit-scrollbar{display:none}
.wtab{flex:0 0 auto;scroll-snap-align:center;position:relative;display:flex;flex-direction:column;align-items:flex-start;gap:1px;padding:7px 14px 8px;min-height:46px;border:0;border-radius:10px;background:transparent;color:var(--muted);font-family:var(--head);cursor:pointer;text-align:left}
.wtab b{font-size:.93rem;font-weight:700;color:var(--ink);white-space:nowrap;line-height:1.2}
.wtab span{font-size:.72rem;white-space:nowrap;line-height:1.2}
.wtab i{display:block;width:100%;height:3px;border-radius:2px;background:var(--line);margin-top:5px;overflow:hidden}
.wtab i::after{content:"";display:block;height:100%;width:calc(var(--p,0) * 100%);background:var(--t);border-radius:2px;transition:width .3s}
.wtab.nobar i{visibility:hidden}
.wtab:hover{background:var(--soft)}
.wtab[aria-selected="true"]{background:var(--soft);box-shadow:inset 0 -3px 0 var(--brand)}
.wtab[aria-selected="true"] b{color:var(--brand)}
.wtab.exam b::after{content:"";display:inline-block;width:7px;height:7px;border-radius:50%;background:var(--focus);margin-left:6px;vertical-align:middle}
.iconbtn{flex:0 0 auto;width:44px;height:44px;border-radius:12px;border:1px solid var(--line);background:var(--surface);color:var(--ink);cursor:pointer;font-size:1.15rem}
.iconbtn:hover{border-color:var(--brand)}
.coursesbtn{flex:0 0 auto;display:inline-flex;align-items:center;gap:6px;height:44px;padding:0 14px;border-radius:12px;border:1px solid var(--line);background:var(--surface);color:var(--ink);font-family:var(--head);font-weight:700;font-size:.9rem;text-decoration:none;white-space:nowrap}
.coursesbtn:hover{border-color:var(--brand);color:var(--brand)}

.shell{display:grid;grid-template-columns:244px minmax(0,1fr);max-width:1280px;margin:0 auto}
.rail{position:sticky;top:var(--topbar-h);align-self:start;height:calc(100vh - var(--topbar-h));overflow:auto;padding:24px 14px 28px 20px}
.rail-title{font-family:var(--head);font-size:.8rem;color:var(--muted);margin:0 0 10px 12px}
.rail a{display:block;padding:7px 12px;margin:0;border-left:2px solid var(--line);border-radius:0 8px 8px 0;color:var(--muted);text-decoration:none;font-family:var(--head);font-size:.9rem;line-height:1.3}
.rail a:hover{color:var(--ink);border-left-color:var(--muted);background:var(--soft)}
.rail a.on{color:var(--brand);border-left-color:var(--brand);font-weight:700;background:var(--soft)}
.rail .prog{margin:18px 12px 0}
.fab,.backdrop{display:none}

main{padding:0 clamp(18px,4vw,56px) 72px}
.hero h1{font-size:clamp(1.9rem,4.2vw,2.8rem);line-height:1.12;max-width:20ch}
.card{box-shadow:0 1px 2px rgba(20,16,40,.05)}
.btn.big{padding:12px 20px;font-size:1rem}

/* home */
.homegrid{display:grid;grid-template-columns:repeat(auto-fill,minmax(260px,1fr));gap:14px;margin-top:14px}
.wcard{display:flex;flex-direction:column;align-items:flex-start;gap:6px;text-align:left;padding:18px;border:1px solid var(--line);border-radius:14px;background:var(--surface);color:var(--ink);cursor:pointer;font:inherit;box-shadow:0 1px 2px rgba(20,16,40,.05);transition:transform .15s,border-color .15s,box-shadow .15s}
.wcard:hover{border-color:var(--brand);transform:translateY(-2px);box-shadow:0 6px 18px rgba(20,16,40,.1)}
.wcard .wnum{font-family:var(--head);font-size:.8rem;color:var(--brand);font-weight:700}
.wcard b{font-family:var(--head);font-size:1.15rem;line-height:1.2}
.wcard .wdesc{font-size:.95rem;line-height:1.5;color:var(--muted)}
.wcard .wtools{font-size:.85rem;font-family:var(--head);color:var(--t)}
.wcard .wprog{display:block;width:100%;height:6px;border-radius:3px;background:var(--line);overflow:hidden;margin-top:6px}
.wcard .wprog i{display:block;height:100%;width:0;background:var(--t);transition:width .3s}
.wcard .wptxt{font-size:.82rem;color:var(--muted);font-family:var(--head)}
.wcard.exam{border-color:var(--focus)}
.wcard.exam .wnum{color:var(--focus)}
ol.steps3{max-width:66ch;padding-left:1.3em}
ol.steps3 li{margin-bottom:.8em}

/* previous / next */
.pager{display:flex;justify-content:space-between;gap:12px;flex-wrap:wrap;margin:36px 0 0;padding-top:20px;border-top:1px solid var(--line)}
.pager button{display:flex;flex-direction:column;gap:2px;padding:12px 18px;min-width:12rem;border:1px solid var(--line);border-radius:12px;background:var(--surface);color:var(--ink);cursor:pointer;font-family:var(--head);text-align:left}
.pager button small{color:var(--muted);font-size:.78rem}
.pager button b{font-size:1rem}
.pager button.next{margin-left:auto;text-align:right;align-items:flex-end}
.pager button:hover{border-color:var(--brand)}

/* small screens: tabs scroll, rail becomes a bottom sheet */
@media (max-width:1000px){
  :root{--topbar-h:108px}
  .topbar-in{flex-wrap:wrap;gap:0 10px;padding:0 12px;min-height:0}
  .brandlink{order:1;flex:1 1 auto;padding:8px 0}
  .iconbtn{order:2;width:40px;height:40px;margin:4px 0}
  .coursesbtn{order:2;height:40px;padding:0 11px;font-size:.82rem}
  .wtabs{order:3;flex:1 0 100%;padding:4px 0 8px;-webkit-mask-image:linear-gradient(to right,transparent 0,#000 14px,#000 calc(100% - 22px),transparent 100%);mask-image:linear-gradient(to right,transparent 0,#000 14px,#000 calc(100% - 22px),transparent 100%)}
  body.scrolled .brandlink,body.scrolled .iconbtn,body.scrolled .coursesbtn{display:none}
  body.scrolled{--topbar-h:66px}
  .shell{grid-template-columns:1fr}
  .rail{position:fixed;left:0;right:0;bottom:0;top:auto;height:auto;max-height:70vh;z-index:60;background:var(--surface);border-top:1px solid var(--line);border-radius:18px 18px 0 0;box-shadow:0 -14px 40px rgba(0,0,0,.28);padding:22px 18px calc(20px + env(safe-area-inset-bottom,0px));transform:translateY(105%);visibility:hidden;transition:transform .25s ease,visibility 0s linear .25s}
  .rail.open{transform:none;visibility:visible;transition:transform .25s ease,visibility 0s}
  .rail::before{content:"";display:block;width:44px;height:4px;border-radius:2px;background:var(--line);margin:-10px auto 14px}
  .rail a{padding:12px 14px;font-size:1rem}
  .fab{display:inline-flex;align-items:center;gap:8px;position:fixed;right:16px;bottom:calc(16px + env(safe-area-inset-bottom,0px));z-index:50;padding:12px 18px;border:0;border-radius:999px;background:var(--brand);color:var(--brand-ink);font-family:var(--head);font-weight:700;font-size:.95rem;box-shadow:0 6px 20px rgba(0,0,0,.3);cursor:pointer}
  .backdrop{display:block;position:fixed;inset:0;z-index:55;background:rgba(10,8,20,.5)}
  .backdrop[hidden]{display:none}
  .pager button{min-width:0;flex:1 1 100%}
  .pager button.next{text-align:left;align-items:flex-start;margin-left:0}
  main{padding-bottom:96px}
}
@media (prefers-reduced-motion:reduce){.rail,.wcard,.wtab i::after,.wcard .wprog i{transition:none}}
.egrid td.diag .gcell[aria-pressed="true"]{background:var(--brand);border-color:var(--brand);color:var(--brand-ink)}

/* ---------- Test 1 mock paper ---------- */
.mtimer{position:sticky;top:var(--topbar-h);z-index:20;display:flex;align-items:center;gap:14px;padding:10px 14px;margin:0 0 14px;background:var(--surface);border:1px solid var(--line);border-radius:12px;box-shadow:0 2px 8px rgba(20,16,40,.08);font-family:var(--head)}
.mtimer b{font-size:1.5rem;font-family:var(--mono);margin-left:auto}
.mtimer.warn{border-color:var(--focus);background:var(--f-bg)}
.mtimer.over{border-color:var(--f);background:var(--f-bg)}
.mtimer.over b{color:var(--f)}
.paper{max-width:820px}
.mhead{display:grid;gap:4px;padding:14px 16px;border:2px solid var(--ink);border-radius:10px;margin-bottom:22px;font-family:var(--head)}
.mhead b{font-size:1.1rem}
.msec h3{margin:26px 0 4px;font-size:1.3rem}
.mrule{font-family:var(--head);color:var(--muted);margin-bottom:12px}
.mq{background:var(--surface);border:1px solid var(--line);border-radius:12px;padding:16px 18px;margin:14px 0}
.mqh{display:flex;justify-content:space-between;align-items:baseline;font-family:var(--head);margin-bottom:6px}
.mqh b{font-size:1.15rem;color:var(--brand)}
.mmarks,.mk{font-family:var(--head);font-size:.82rem;color:var(--muted);white-space:nowrap}
.mq p{max-width:none}
.mq-list{max-width:none;padding-left:1.6em}
.mq-list li{margin-bottom:.7em}
.mfig{display:flex;justify-content:center;margin:8px 0}
.mfig .dg{max-width:300px}
.mocktab td,.mocktab th{padding:5px 12px;font-size:.95rem}
.mkey{margin-top:14px}
.keybox{background:var(--t-bg);border-left:4px solid var(--t);border-radius:0 10px 10px 0;padding:6px 16px 12px}
.keybox h4{font-family:var(--head);margin:12px 0 6px;font-size:1rem;color:var(--t)}
.proofkey{margin:6px 0 10px}
.proofkey .pl{display:grid;grid-template-columns:minmax(0,1fr) auto;gap:14px;padding:5px 0;border-bottom:1px dashed var(--line);align-items:baseline}
.proofkey .pl .why{font-family:var(--head);font-size:.85rem;color:var(--muted);text-align:right}
.scheme{display:grid;gap:2px}
.srow{display:flex;justify-content:space-between;align-items:center;gap:14px;padding:6px 0;border-bottom:1px dashed var(--line);font-size:.95rem}
.srow select{flex:0 0 auto}
.mqsum{margin:10px 0 0;font-family:var(--head)}
.mfoot{margin:24px 0}
#w7-result h3{font-family:var(--head)}
@media (max-width:1000px){.proofkey .pl{grid-template-columns:1fr}.proofkey .pl .why{text-align:left}.mtimer b{font-size:1.25rem}}
@media print{
  body.printing-paper .topbar,body.printing-paper .rail,body.printing-paper .fab,body.printing-paper .backdrop,body.printing-paper .pager,body.printing-paper .week:not(#week7),body.printing-paper #w7-top,body.printing-paper #w7-paperwrap > h2,body.printing-paper .mtimer,body.printing-paper .mfoot,body.printing-paper .mkey,body.printing-paper #w7-result,body.printing-paper #w7-paperhint,body.printing-paper .skip{display:none!important}
  body.printing-paper{background:#fff;color:#000}
  body.printing-paper .shell{display:block}
  body.printing-paper main{padding:0}
  body.printing-paper .mq{break-inside:avoid;border:1px solid #888;box-shadow:none}
  body.printing-paper section{border:0;padding:0}
}
@media print{
  body.printing-paper .msec h3,body.printing-paper .mrule{break-after:avoid}
  body.printing-paper .msec + .msec{break-before:page}
}

/* =====================================================
   COURSE FAMILY THEME: matches the Computer Organisation and
   Programming sites. Paper + ink, IBM Plex, hairline rules, square corners.
   ===================================================== */
:root{
  --bg:#f3efe6; --surface:#faf8f2; --ink:#17150f; --muted:#5f5a4b; --line:#d8d1bf;
  --brand:#6b2fa0; --brand-ink:#ffffff; --soft:#ece6d8;
  --t:#1d7a6c; --t-bg:#dcebe4; --f:#c0262d; --f-bg:#f7dcd8; --focus:#d9480f;
  --grid:rgba(23,21,15,.045);
  --head:"IBM Plex Sans",system-ui,sans-serif;
  --body:"IBM Plex Sans",system-ui,sans-serif;
  --serif:"IBM Plex Serif",Georgia,serif;
  --mono:"IBM Plex Mono",ui-monospace,Consolas,monospace;
  color-scheme:light;
}
@media (prefers-color-scheme: dark){
  :root:not([data-theme="light"]){
    --bg:#111110; --surface:#181816; --ink:#ece7da; --muted:#a9a395; --line:#2f2e2a;
    --brand:#b58ce8; --brand-ink:#111110; --soft:#22211e;
    --t:#6fd0bf; --t-bg:#15302b; --f:#ff7b7b; --f-bg:#341b1b; --focus:#ff7a3d;
    --grid:rgba(236,231,218,.035); color-scheme:dark;
  }
}
:root[data-theme="dark"]{
  --bg:#111110; --surface:#181816; --ink:#ece7da; --muted:#a9a395; --line:#2f2e2a;
  --brand:#b58ce8; --brand-ink:#111110; --soft:#22211e;
  --t:#6fd0bf; --t-bg:#15302b; --f:#ff7b7b; --f-bg:#341b1b; --focus:#ff7a3d;
  --grid:rgba(236,231,218,.035); color-scheme:dark;
}
body{font-size:1rem;line-height:1.65;-webkit-font-smoothing:antialiased;background-color:var(--bg);background-image:linear-gradient(var(--grid) 1px,transparent 1px),linear-gradient(90deg,var(--grid) 1px,transparent 1px);background-size:24px 24px}
::selection{background:var(--brand);color:var(--brand-ink)}
h1,h2,h3{font-family:var(--serif);font-weight:600;letter-spacing:-.01em}
h3{font-family:var(--head);font-size:1.1rem}
.hero h1{font-weight:500;line-height:1.08}
.hero .lead{color:var(--muted)}
:focus-visible{border-radius:0}

/* square everything */
.card,.trap,.tip,.idea,pre.code,.btn,.keys button,select,input[type=text],.player,.pl-code,.cell .box,
.verdict-box,.det,.fb,.q,.q textarea,.hint,.sol,.tog,.tab,.sorter button,.pending,.gcell,.mxarea,
#w6-mock-box .xq,details,.skip,.brandlink,.brandlink .mark,.wtab,.wtab i,.wtab i::after,.iconbtn,.coursesbtn,
.rail a,.rail,.wcard,.wcard .wprog,.pager button,.mtimer,.mhead,.mq,.keybox,.lvl,.vars span,.ptag,.bar,.fab{border-radius:0}
.card,.wcard,.mtimer,.fab,.rail{box-shadow:none}
.trap,.tip,.idea,.fb,.sol,.keybox{border-left-width:3px}

/* buttons and inputs */
.btn,.keys button{font-family:var(--mono);font-size:.82rem;font-weight:500;text-transform:uppercase;letter-spacing:.05em;border:1px solid var(--ink);background:transparent;padding:8px 14px}
.btn:hover:not(:disabled){background:var(--ink);color:var(--surface);border-color:var(--ink)}
.btn.primary{background:var(--brand);border-color:var(--brand);color:var(--brand-ink)}
.btn.primary:hover:not(:disabled){background:var(--ink);border-color:var(--ink);color:var(--surface)}
.btn.big{padding:11px 18px;font-size:.85rem}
select,input[type=text],.q textarea,.mxarea{border:1px solid var(--line);background:var(--surface)}
select:focus,input[type=text]:focus,.q textarea:focus,.mxarea:focus{border-color:var(--ink);outline:none}
.tog{font-family:var(--mono);font-size:.9rem}
.tab{border:1px solid var(--line)}
.tab[aria-selected="true"]{background:var(--ink);border-color:var(--ink);color:var(--surface)}
.lvl,.ptag{font-family:var(--mono);font-size:.72rem;text-transform:uppercase;letter-spacing:.05em}
.vars span{font-family:var(--mono)}
th{font-family:var(--mono);font-size:.85rem}

/* top bar */
:root{--topbar-h:64px}
.topbar{background:var(--surface);border-bottom:2px solid var(--ink)}
.topbar-in{min-height:62px;align-items:stretch;gap:20px}
.brandlink .mark{width:auto;height:auto;padding:3px 8px 2px;background:var(--ink);color:var(--surface);border-bottom:3px solid var(--brand);font-size:1rem}
.brandlink .bt b{font-weight:600;font-size:.95rem}
.brandlink .bt span{font-family:var(--mono);font-size:.68rem}
.wtabs{gap:0;padding:0;align-items:stretch}
.wtab{min-height:0;padding:10px 13px 8px;justify-content:center;background:transparent;border-bottom:3px solid transparent;margin-bottom:-2px}
.wtab b{font-weight:500;font-size:.88rem;color:var(--muted)}
.wtab span{font-family:var(--mono);font-size:.66rem}
.wtab i{height:2px;margin-top:4px}
.wtab:hover{background:transparent}
.wtab:hover b{color:var(--ink)}
.wtab[aria-selected="true"]{background:transparent;box-shadow:none;border-bottom-color:var(--brand)}
.wtab[aria-selected="true"] b{color:var(--ink);font-weight:600}
.wtab.exam b::after{border-radius:0;width:6px;height:6px}
.iconbtn,.coursesbtn{align-self:center;height:32px;border:1px solid var(--ink);background:transparent;color:var(--ink)}
.iconbtn{width:32px;display:grid;place-items:center;padding:0}
.iconbtn svg{width:16px;height:16px}
.coursesbtn{font-family:var(--mono);font-weight:500;font-size:.72rem;text-transform:uppercase;letter-spacing:.06em;padding:0 10px}
.iconbtn:hover,.coursesbtn:hover{background:var(--ink);color:var(--surface);border-color:var(--ink)}

/* side rail */
.rail-title{font-family:var(--mono);font-size:.68rem;text-transform:uppercase;letter-spacing:.08em}
.rail a{font-size:.86rem}
.rail a:hover{background:transparent;border-left-color:var(--ink)}
.rail a.on{background:transparent;color:var(--ink);font-weight:600;border-left:3px solid var(--brand)}
.prog{font-family:var(--mono);font-size:.72rem}
.bar{height:4px}

/* home cards */
.wcard{border-top:3px solid var(--ink)}
.wcard:hover{border-color:var(--line);border-top-color:var(--brand);box-shadow:0 10px 24px -14px rgba(0,0,0,.45)}
.wcard .wnum{font-family:var(--mono);font-weight:500;font-size:.72rem;text-transform:uppercase;letter-spacing:.06em}
.wcard b{font-family:var(--serif);font-weight:600;font-size:1.2rem}
.wcard .wtools,.wcard .wptxt{font-family:var(--mono);font-size:.72rem}
.wcard .wprog{height:4px}
.wcard.exam{border-color:var(--line);border-top-color:var(--focus)}

/* pager, mock paper */
.pager button small{font-family:var(--mono);text-transform:uppercase;letter-spacing:.06em;font-size:.68rem}
.pager button b{font-family:var(--serif);font-weight:600}
.pager button:hover{border-color:var(--ink)}
.mqh b{font-family:var(--serif)}
.mmarks,.mk,.mrule{font-family:var(--mono);font-size:.75rem}

@media (max-width:1000px){
  :root{--topbar-h:96px}
  body.scrolled{--topbar-h:48px}
  .topbar-in{align-items:center;gap:0 8px}
  .brandlink{padding:10px 0}
  .iconbtn,.coursesbtn{margin:0;height:32px}
  .iconbtn{width:32px}
  .wtabs{align-self:stretch}
  .wtab{padding:6px 11px}
  .rail{border-top:2px solid var(--ink)}
  .rail::before{border-radius:0;background:var(--ink)}
  .fab{background:var(--ink);color:var(--surface);font-family:var(--mono);font-weight:500;font-size:.78rem;text-transform:uppercase;letter-spacing:.06em;border-bottom:3px solid var(--brand)}
}

/* footer credit */
.sitefoot{max-width:1280px;margin:0 auto;display:flex;flex-wrap:wrap;justify-content:space-between;gap:8px 20px;padding:18px 20px 28px;border-top:1px solid var(--line);font:.75rem var(--mono);color:var(--muted)}
.ig-credit{display:inline-flex;align-items:center;gap:6px;color:var(--ink);text-decoration:none;font-weight:500}
.ig-credit:hover{color:var(--brand);text-decoration:underline}
@media (max-width:1000px){.sitefoot{padding-bottom:96px}}
/* phone header: let the course name shrink so the buttons stay on one line */
@media (max-width:1000px){
  .brandlink{min-width:0;flex:1 1 0}
  .brandlink .bt{min-width:0}
  .brandlink .bt b,.brandlink .bt span{overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
}