/* MultiplicationChart.com */
@font-face{font-family:"Lexend";src:url("lexend.woff2") format("woff2");font-weight:100 900;font-display:swap}
:root{
  --ink:#16264a; --ink-soft:#4a5878; --paper:#ffffff; --wash:#f3f8fc;
  --sky:#d6ecf8; --sky-deep:#b9def2; --blue:#2b6cb8; --blue-deep:#1d4f8c;
  --pink:#f9bfd2; --sun:#ffd43b; --green:#1f9d63; --green-soft:#c9f0dc; --red:#d6455d; --red-soft:#fbd3da;
  --line:#dbe6f0; --radius:14px;
  --font:"Lexend",ui-rounded,"Segoe UI",system-ui,-apple-system,Roboto,Helvetica,Arial,sans-serif;
}
*{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;-webkit-tap-highlight-color:transparent;scroll-behavior:smooth;scroll-padding-top:70px}
body{margin:0;font-family:var(--font);color:var(--ink);background:var(--paper);font-size:17px;line-height:1.65;font-weight:350}
a{color:var(--blue-deep);text-underline-offset:3px}
a:hover{color:var(--blue)}
:focus-visible{outline:3px solid var(--sun);outline-offset:2px;border-radius:6px}
.wrap{max-width:1240px;margin:0 auto;padding:0 20px}
.skip{position:absolute;left:-999px;top:8px;background:var(--ink);color:#fff;padding:8px 14px;border-radius:8px;z-index:50}
.skip:focus{left:8px}
.vh{position:absolute;width:1px;height:1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap}

/* header */
.top{position:sticky;top:0;z-index:20;background:rgba(255,255,255,.94);backdrop-filter:blur(8px);border-bottom:1px solid var(--line)}
.top .wrap{display:flex;align-items:center;gap:22px;height:56px}
.logo{display:flex;align-items:center;gap:10px;font-weight:700;font-size:18px;color:var(--ink);text-decoration:none;white-space:nowrap;letter-spacing:-.01em}
.logo svg{width:30px;height:30px;flex:none}
.logo span span{color:var(--blue)}
.logo i{font-style:normal;font-weight:500;color:var(--ink-soft)}
.nav{display:flex;gap:4px;overflow-x:auto;scrollbar-width:none;margin-left:auto}
.nav::-webkit-scrollbar{display:none}
.nav a{padding:7px 12px;border-radius:999px;text-decoration:none;color:var(--ink);font-size:15px;font-weight:500;white-space:nowrap}
.nav a:hover{background:var(--wash)}
.nav a[aria-current=page]{background:var(--ink);color:#fff}

/* hero and tool */
.hero{background-color:var(--wash);background-image:linear-gradient(#e2edf6 1px,transparent 1px),linear-gradient(90deg,#e2edf6 1px,transparent 1px);background-size:28px 28px;border-bottom:1px solid var(--line);padding:18px 0 30px}
.hero.inner{--top:192px}
.crumbs{font-size:14px;color:var(--ink-soft);margin:0 0 4px}
.crumbs a{color:inherit}
.titlebar{display:flex;flex-wrap:wrap;align-items:end;justify-content:space-between;gap:10px 24px;margin-bottom:14px}
h1{font-size:clamp(26px,3.4vw,38px);line-height:1.1;margin:0;font-weight:750;letter-spacing:-.02em}
.lead{margin:6px 0 0;color:var(--ink-soft);font-size:16px;max-width:60ch}
.sizes{display:flex;flex-wrap:wrap;gap:5px;align-items:center}
.sizes .lbl{font-size:14px;color:var(--ink-soft);margin-right:2px}
.chip{display:inline-flex;align-items:center;justify-content:center;min-height:38px;padding:0 11px;border-radius:999px;background:#fff;border:2px solid var(--line);color:var(--ink);font:600 15px var(--font);text-decoration:none;cursor:pointer}
.chip:hover{border-color:var(--blue);color:var(--blue-deep)}
.chip[aria-current=page],.chip[aria-pressed=true]{background:var(--blue);border-color:var(--blue);color:#fff}
.custom{display:inline-flex;align-items:center;border:2px solid var(--line);border-radius:999px;background:#fff;overflow:hidden;min-height:38px}
.custom label{font-size:14px;padding-left:12px;color:var(--ink-soft)}
.custom input{width:60px;border:0;font:600 15px var(--font);color:var(--ink);padding:6px 6px 6px 8px;background:transparent;text-align:center}
.custom input:focus{outline:none}
.custom input::-webkit-inner-spin-button{opacity:1;cursor:pointer;margin-left:4px;height:26px}
.custom:focus-within{border-color:var(--blue);box-shadow:0 0 0 3px rgba(43,108,184,.22)}
.custom button{border:0;background:var(--ink);color:#fff;font:600 14px var(--font);padding:0 12px;align-self:stretch;cursor:pointer}

.stage{display:grid;gap:18px}
.chart-col{min-width:0;background:#fff}
.chart-wrap{--g:2px;--p:8px;container-type:inline-size;width:100%;border-radius:var(--radius);background:#fff;padding:var(--p) calc(var(--p) - var(--g)) calc(var(--p) - var(--g)) var(--p);box-shadow:0 1px 0 var(--line),0 12px 30px -18px rgba(22,38,74,.35);border:1px solid var(--line);outline-offset:3px}
.chart-wrap.scroll{overflow:auto;max-height:76vh;-webkit-overflow-scrolling:touch;overscroll-behavior:contain}
/* scrolling charts: the white frame is a border (not padding) so numbers can never slide past the sticky headers */
.chart-wrap.scroll{padding:0;border:solid #fff;border-width:var(--p) calc(var(--p) - var(--g)) calc(var(--p) - var(--g)) var(--p);box-shadow:0 0 0 1px var(--line),0 12px 30px -18px rgba(22,38,74,.35)}
.scroll .mc th{background:#fff}
.scroll .mc th::before{content:"";position:absolute;inset:0;z-index:-1;border-radius:inherit;background:var(--blue)}
.scroll .mc th.on::before,.scroll .mc th.corner::before{background:var(--ink)}
table.mc{border-collapse:separate;border-spacing:0;table-layout:fixed;width:100%;font-weight:600;font-variant-numeric:tabular-nums;user-select:none;-webkit-user-select:none}
.mc th,.mc td{padding:0;text-align:center;vertical-align:middle;border-right:var(--g) solid #fff;border-bottom:var(--g) solid #fff;height:2.3em;height:calc(100cqw/(var(--n) + 1));font-size:calc(100cqw/(var(--n) + 1)*.4);line-height:1;overflow:hidden;position:relative;scroll-margin:60px}
.mc td{background:var(--sky);cursor:pointer;border-radius:4px}
.mc td.sq{background:var(--sky-deep)}
.mc th{background:var(--blue);color:#fff;font-weight:700;cursor:pointer;border-radius:4px}
.mc th.corner{background:var(--ink);cursor:default}
.mc thead th{position:sticky;top:0;z-index:2}
.mc tbody th{position:sticky;left:0;z-index:1}
.mc thead th.corner{left:0;z-index:3}
.scroll table.mc{width:calc(var(--cell)*(var(--n) + 1))}
.scroll .mc th,.scroll .mc td{height:var(--cell);font-size:var(--fs)}
.mc td.path{background:var(--pink)}
.mc th.on{background:var(--ink)}
.mc td.target{background:var(--sun);box-shadow:inset 0 0 0 3px var(--ink);z-index:1}
.mc td.pat{background:#ffe48a}
.mc td.dim{background:#eef4f8;color:#9aa8bd}
.mc.blank td{color:transparent}
.mc.blank td.ok{color:var(--ink);background:var(--green-soft)}
.mc.blank td.shown{color:var(--ink-soft)}
.mc.blank td.path{background:var(--pink)}
.mc.blank td.target{background:var(--sun)}
.mc td.bad{background:var(--red-soft)!important;animation:shake .3s}
.mc td input{position:absolute;inset:0;width:100%;height:100%;border:0;background:transparent;text-align:center;font:inherit;font-weight:700;color:var(--ink);padding:0;outline:none;-moz-appearance:textfield}
@keyframes shake{25%{transform:translateX(-3px)}75%{transform:translateX(3px)}}

.panel{display:grid;gap:14px;align-content:start;min-width:0}
.card{background:#fff;border:1px solid var(--line);border-radius:var(--radius);padding:16px}
.card h2{font-size:14px;font-weight:600;color:var(--ink-soft);margin:0 0 10px;letter-spacing:0}
.readout{container-type:inline-size;min-height:154px;display:flex;flex-direction:column;justify-content:center;text-align:center;border:2px solid var(--ink)}
.eq{font-size:calc(clamp(30px,13cqw,60px)*var(--eqs,1));font-weight:750;line-height:1.1;white-space:nowrap;letter-spacing:-.02em;font-variant-numeric:tabular-nums}
.eq b{background:var(--sun);padding:0 .18em;border-radius:8px;font-weight:inherit}
.eq.stack b{display:table;margin:8px auto 0}
.eq.idle{white-space:normal;font-size:19px;font-weight:500;color:var(--ink-soft);letter-spacing:0;line-height:1.4}
.sub{margin:8px 0 0;font-size:15px;color:var(--ink-soft);line-height:1.4;min-height:2.8em}
.sub:empty{display:none}
.eq.idle+.sub{min-height:0}
#quiz{container-type:inline-size}
.seg{display:grid;grid-template-columns:repeat(3,1fr);background:var(--wash);border-radius:12px;padding:4px;gap:4px}
.seg button{border:0;border-radius:9px;background:transparent;font:600 15px var(--font);color:var(--ink);min-height:42px;cursor:pointer}
.seg button[aria-pressed=true]{background:var(--ink);color:#fff}
.printcard{border:2px solid var(--ink)}
.printcard h2{font-size:20px;font-weight:700;color:var(--ink);margin:0 0 4px}
.plabel{font-size:14px;color:var(--ink-soft);margin:12px 0 6px}
.seg.two{grid-template-columns:1fr 1fr}
.pgo{margin-top:16px}
.pgo .btn{flex:1 1 130px;min-height:50px;font-size:16px;white-space:nowrap;padding:0 12px}
.printpage .readout{border:1px solid var(--line)}
[data-cur=quiz] .printcard{display:none}
.modehint{font-size:14.5px;color:var(--ink-soft);margin:10px 0 0;line-height:1.45}
.row{display:flex;flex-wrap:wrap;gap:8px}
.btn{display:inline-flex;align-items:center;justify-content:center;gap:8px;min-height:44px;padding:0 16px;border-radius:12px;border:2px solid var(--ink);background:#fff;color:var(--ink);font:600 15px var(--font);text-decoration:none;cursor:pointer}
.btn:hover{background:var(--wash);color:var(--ink)}
.btn.primary{background:var(--ink);color:#fff}
.btn.primary:hover{background:var(--blue-deep)}
.btn svg{width:18px;height:18px;flex:none}
.opts{display:grid;grid-template-columns:1fr 1fr;gap:8px;margin-top:6px}
.opts button{min-height:64px;border-radius:12px;border:2px solid var(--line);background:#fff;font:700 24px var(--font);color:var(--ink);cursor:pointer;font-variant-numeric:tabular-nums}
.opts button:hover{border-color:var(--blue)}
.opts button.right{background:var(--green-soft);border-color:var(--green)}
.opts button.wrong{background:var(--red-soft);border-color:var(--red)}
.stats{display:flex;justify-content:center;gap:22px;margin-top:12px;font-size:15px;color:var(--ink-soft)}
.stats strong{color:var(--ink);font-weight:700}
.bar{height:10px;border-radius:99px;background:var(--wash);overflow:hidden;margin:10px 0}
.bar i{display:block;height:100%;width:0;background:var(--green);border-radius:99px;transition:width .25s}
[hidden]{display:none!important}

@media (min-width:900px){
  .stage{grid-template-columns:auto minmax(340px,1fr);gap:28px;align-items:start}
  .chart-col{width:min(calc(100vw - 340px - 28px - 40px),calc(100vh - var(--top,166px)),832px);min-width:440px;border-radius:var(--radius)}
  .chart-wrap.scroll{max-height:calc(100vh - var(--top,166px));min-height:440px}
  .panel{position:sticky;top:70px}
  .card{padding:14px 16px}
}
@media (min-width:1280px){
  h1{font-size:36px;white-space:nowrap}
  .titlebar{flex-wrap:nowrap}
  .titlebar>div{flex:1 1 0;min-width:0}
  .sizes{flex:none;justify-content:flex-end}
}
@media (max-width:899px){
  .panel{grid-template-columns:1fr}
  .readout{min-height:136px}
  .stage{display:flex;flex-direction:column}
  .panel{display:contents}
  .printpage .readout{order:2}
  .printcard{order:0}.readout,#quiz{order:1}.chart-col{order:2}.modes{order:3}.pats{order:4}.actions{order:5}
  .sizes{flex-wrap:nowrap;overflow-x:auto;scrollbar-width:none;margin:0 -20px;padding:2px 20px;width:calc(100% + 40px)}
  .sizes::-webkit-scrollbar{display:none}
  .sizes>*{flex:none}
  .chart-wrap{--g:1px;--p:6px}
  .mc th,.mc td{border-radius:3px}
}
@media (max-width:560px){
  .logo{font-size:16px}.logo svg{width:26px;height:26px}
  .top .wrap{gap:10px}
  .wrap{padding:0 12px}
  .sizes{margin:0 -12px;padding:2px 12px;width:calc(100% + 24px)}
  .chart-wrap{--p:4px;border-radius:10px}
}
.stage:fullscreen{background:var(--wash);padding:3vmin;overflow:auto;align-content:center;justify-content:center}
.stage:fullscreen .chart-col{width:min(calc(100vw - 6vmin),calc(100vh - 6vmin));min-width:0;margin:0 auto}
.stage:fullscreen .pats,.stage:fullscreen .printcard,.stage:fullscreen .actions h2,.stage:fullscreen .actions .btn:not(#btnFull){display:none}
@media (min-width:900px){
  .stage:fullscreen{grid-template-columns:auto minmax(340px,520px)}
  .stage:fullscreen .chart-col{width:min(calc(100vw - 6vmin - 28px - 340px),calc(100vh - 6vmin))}
  .stage:fullscreen .panel{position:static;align-self:center}
  .stage:fullscreen #quiz .eq{font-size:clamp(40px,15cqw,84px)}
  .stage:fullscreen .opts button{min-height:96px;font-size:34px}
}
.fsx{display:none;position:absolute;top:10px;right:10px;z-index:5;width:44px;height:44px;border-radius:50%;border:2px solid var(--ink);background:#fff;color:var(--ink);font:400 28px/1 var(--font);cursor:pointer;align-items:center;justify-content:center;padding:0 0 3px}
.fsx:hover{background:var(--ink);color:#fff}
.chart-col:fullscreen .fsx{display:flex}
@media (max-aspect-ratio:1/1){.chart-col:fullscreen{padding-top:60px!important}}
@media (min-aspect-ratio:1/1){.chart-col:fullscreen:has(.scroll){padding-right:64px!important}}
.stage:fullscreen .chart-wrap.scroll{max-height:calc(100vh - 6vmin)}
.chart-col:fullscreen{display:flex;align-items:center;justify-content:center;padding:1.5vmin;background:#fff}
.chart-col:fullscreen .chart-wrap{width:97vmin;box-shadow:none;border:0}
.chart-col:fullscreen .chart-wrap.scroll{width:100%;max-height:100%}

/* content */
.content{padding-top:50px;padding-bottom:20px}
.prose{max-width:76ch}
.content section{margin-bottom:56px}
h2{font-size:clamp(23px,2.6vw,30px);line-height:1.2;margin:0 0 14px;font-weight:700;letter-spacing:-.015em}
h3{font-size:19px;margin:26px 0 6px;font-weight:650}
.prose p{margin:0 0 14px}
.steps{list-style:none;padding:0;margin:20px 0 0;display:grid;gap:14px;grid-template-columns:repeat(auto-fit,minmax(230px,1fr));counter-reset:s}
.steps li{counter-increment:s;background:var(--wash);border-radius:var(--radius);padding:18px 18px 18px 64px;position:relative}
.steps li::before{content:counter(s);position:absolute;left:16px;top:16px;width:36px;height:36px;border-radius:10px;background:var(--blue);color:#fff;font-weight:700;display:grid;place-items:center}
.steps strong{display:block;margin-bottom:2px}
.tables{display:grid;grid-template-columns:repeat(auto-fill,minmax(168px,1fr));gap:14px;margin-top:20px}
.tt{border:1px solid var(--line);border-radius:var(--radius);overflow:hidden;background:#fff}
.tt h3{margin:0;background:var(--blue);color:#fff;font-size:16px;padding:9px 14px;font-weight:650}
.tt ul{list-style:none;margin:0;padding:8px 14px 12px;font-variant-numeric:tabular-nums;font-size:16px;line-height:1.75}
.tt li b{font-weight:700}
.cards{display:grid;grid-template-columns:repeat(auto-fill,minmax(250px,1fr));gap:14px;margin-top:20px}
.cards a{display:block;border:2px solid var(--line);border-radius:var(--radius);padding:16px 18px;text-decoration:none;color:var(--ink);background:#fff}
.cards a:hover{border-color:var(--blue)}
.cards strong{display:block;font-size:17.5px;font-weight:650}
.cards span{font-size:15px;color:var(--ink-soft);line-height:1.45;display:block;margin-top:3px}
.dl{width:100%;border-collapse:collapse;margin-top:18px;max-width:760px}
.dl th,.dl td{text-align:left;padding:11px 10px;border-bottom:1px solid var(--line);font-size:16px}
.dl th{font-weight:600}
.dl thead th{font-size:14px;color:var(--ink-soft);font-weight:500}
.dl a{font-weight:600;white-space:nowrap}
.grades{display:grid;gap:12px;grid-template-columns:repeat(auto-fit,minmax(220px,1fr));margin-top:18px}
.grades div{border-left:5px solid var(--sun);background:var(--wash);padding:14px 16px;border-radius:0 var(--radius) var(--radius) 0}
.grades strong{display:block}
.grades p{margin:4px 0 0;font-size:15.5px;line-height:1.5}
.faq details{border-bottom:1px solid var(--line);max-width:76ch}
.faq summary{cursor:pointer;padding:15px 30px 15px 0;font-weight:600;list-style:none;position:relative}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:"+";position:absolute;right:4px;top:11px;font-size:24px;color:var(--blue);font-weight:400}
.faq details[open] summary::after{content:"\2212"}
.faq details p{margin:0 0 16px}

footer{background:var(--ink);color:#c9d4ea;margin-top:30px;padding:44px 0 26px;font-size:15.5px}
footer a{color:#fff;text-decoration:none}
footer a:hover{text-decoration:underline;color:#fff}
.fgrid{display:grid;gap:30px;grid-template-columns:1.5fr repeat(3,1fr)}
.fgrid h2{font-size:15px;color:#fff;margin:0 0 10px;font-weight:600}
.fgrid ul{list-style:none;margin:0;padding:0;display:grid;gap:7px}
.fgrid p{margin:10px 0 0;max-width:38ch;line-height:1.55}
footer .logo{color:#fff}
footer .logo span span{color:var(--sun)}
footer .logo i{color:#c9d4ea}
.legal{border-top:1px solid rgba(255,255,255,.15);margin-top:34px;padding-top:18px;display:flex;flex-wrap:wrap;gap:8px 20px;justify-content:space-between;font-size:14px}
@media (max-width:800px){.fgrid{grid-template-columns:1fr 1fr}.fgrid>div:first-child{grid-column:1/-1}}

#printArea{display:none}
@media (prefers-reduced-motion:reduce){*{animation:none!important;transition:none!important;scroll-behavior:auto!important}}

@media print{
  body>*:not(#printArea){display:none!important}
  body{background:#fff}
  #printArea{display:block}
  .pp{break-after:page;page-break-after:always;text-align:center}
  .pp:last-child{break-after:auto;page-break-after:auto}
  .pp h1{font-size:17pt;margin:0 0 4mm;color:#000}
  .pp table{max-width:100%;border-collapse:collapse;margin:0 auto;table-layout:fixed;font-weight:600;font-variant-numeric:tabular-nums;-webkit-print-color-adjust:exact;print-color-adjust:exact}
  .pp th,.pp td{border:.35mm solid #33415f;padding:0;text-align:center;line-height:1;color:#000;overflow:hidden}
  .pp th{background:#cfe3f5;font-weight:800}
  .pp td.sq{background:#edf1f6}
  .pp .foot{font-size:8pt;color:#555;margin-top:3mm}
}
@media (min-width:900px) and (max-width:1279px){.hero{--top:212px}.hero.inner{--top:238px}}