@font-face{font-family:Lexend;font-style:normal;font-display:swap;font-weight:400;src:url(/assets/lexend-latin-400-normal-CwRJVcUA.woff2)format("woff2"),url(/assets/lexend-latin-400-normal-CHypAkT3.woff)format("woff")}@font-face{font-family:Lexend;font-style:normal;font-display:swap;font-weight:500;src:url(/assets/lexend-latin-500-normal-Dl-X5nog.woff2)format("woff2"),url(/assets/lexend-latin-500-normal-D9x1QWTH.woff)format("woff")}@font-face{font-family:Lexend;font-style:normal;font-display:swap;font-weight:600;src:url(/assets/lexend-latin-600-normal-DdvlkEkX.woff2)format("woff2"),url(/assets/lexend-latin-600-normal-DSBzZxpA.woff)format("woff")}:root{--canvas:#fbf7f0;--ink:#2e2a25;--ink-soft:#6b6358;--key:#fff;--key-border:#e8e1d5;--key-edge:#dcd3c4;--hover:#2e2a250f;--success-fill:#e3f4ea;--success-ink:#1f7a4d;--success-edge:#9ed4b5;--warn-fill:#fcefd9;--warn-ink:#8a5a12;--warn-edge:#e0a84a;--info-fill:#e4eefb;--info-ink:#1d5fa8;--info-edge:#a9c8ee;--radius-key:14px;--radius-tile:20px;--lightningcss-light:initial;--lightningcss-dark: ;color-scheme:light;color:var(--ink);background:var(--canvas);-webkit-text-size-adjust:100%;font-family:Lexend,system-ui,sans-serif}[data-mode=add]{--mode-fill:#ddf3ea;--mode-ink:#0f6e56;--mode-edge:#9fd9c2;--mode-strong:#1d9e75}[data-mode=sub]{--mode-fill:#fbe6de;--mode-ink:#993c1d;--mode-edge:#f0b9a4;--mode-strong:#d85a30}[data-mode=mul]{--mode-fill:#e9e7fc;--mode-ink:#534ab7;--mode-edge:#c3bef2;--mode-strong:#7f77dd}[data-mode=div]{--mode-fill:#faeed6;--mode-ink:#854f0b;--mode-edge:#f0cf8e;--mode-strong:#ba7517}*,:before,:after{box-sizing:border-box}html,body{background:var(--canvas);min-height:100%;margin:0}html{overscroll-behavior:none;touch-action:manipulation}body{-webkit-user-select:none;user-select:none;-webkit-touch-callout:none}button{font:inherit;color:inherit;cursor:pointer;touch-action:manipulation;-webkit-tap-highlight-color:transparent}button:focus-visible{outline:3px solid var(--info-ink);outline-offset:2px}.screen{max-width:1100px;min-height:100dvh;padding:max(16px, env(safe-area-inset-top)) max(16px, env(safe-area-inset-right)) max(16px, env(safe-area-inset-bottom)) max(16px, env(safe-area-inset-left));flex-direction:column;gap:16px;margin:0 auto;display:flex}.icon-button{width:44px;height:44px;color:var(--ink-soft);background:0 0;border:none;border-radius:12px;justify-content:center;align-items:center;font-size:24px;display:inline-flex}@media (hover:hover){.icon-button:hover{background:var(--hover)}}@keyframes arm{0%{pointer-events:none}}.topbar{justify-content:space-between;align-items:center;gap:12px;min-height:44px;display:flex}.topbar__start{align-items:center;gap:12px;min-width:0;display:flex}.chooser__title{margin:0;font-size:20px;font-weight:600}.chooser__grid{grid-template-columns:repeat(2,minmax(0,1fr));gap:clamp(12px,3vmin,24px);width:min(640px,100%,100dvh - 140px);margin:auto;display:grid}.tile{aspect-ratio:1;border:none;border-bottom:4px solid var(--mode-edge);border-radius:var(--radius-tile);background:var(--mode-fill);color:var(--mode-ink);justify-content:center;align-items:center;font-size:clamp(56px,14vmin,120px);font-weight:500;line-height:1;transition:transform 80ms ease-out,border-bottom-width 80ms ease-out;display:flex}.tile:active{border-bottom-width:1px;transform:translateY(3px)}.answer{border:.05em solid var(--mode-edge);min-width:2.2em;height:1.4em;color:var(--mode-ink);background:#fff;border-radius:.22em;justify-content:center;align-items:center;padding:0 .25em;display:inline-flex}.problem--stacked .answer{min-width:calc(var(--answer-cells,2) * .64em + .6em);justify-content:flex-end}.answer__placeholder{color:#c9bfae}.answer--correct{background:var(--success-fill);border-color:var(--success-edge);color:var(--success-ink)}.answer--wrong{background:var(--warn-fill);border-color:var(--warn-edge);color:var(--warn-ink)}.answer--revealed{background:var(--info-fill);border-color:var(--info-edge);color:var(--info-ink)}.feedback{text-align:center;flex-direction:column;align-items:center;gap:20px;display:flex}.feedback__message{color:var(--ink-soft);margin:0;font-size:clamp(24px,4dvh,34px);font-weight:600}.feedback--correct .feedback__message{color:var(--success-ink)}.feedback__actions{gap:12px;width:100%;display:flex}.action{height:var(--key-h,64px);border:1px solid var(--key-border);border-bottom:4px solid var(--key-edge);border-radius:var(--radius-key);background:var(--key);flex:1;justify-content:center;align-items:center;gap:8px;font-size:clamp(18px,3dvh,24px);font-weight:500;transition:transform 60ms ease-out,border-bottom-width 60ms ease-out;display:inline-flex}.action:active{border-bottom-width:1px;transform:translateY(3px)}.feedback--correct .action--primary{border-color:var(--success-ink);background:var(--success-ink);color:#fff;border-bottom-color:#145236}.feedback--revealed .action--primary{border-color:var(--info-ink);background:var(--info-ink);color:#fff;border-bottom-color:#133f70}.feedback__actions{animation:.25s ease-out feedback-in,.4s step-end arm}@keyframes feedback-in{0%{opacity:0}}.pad{grid-template-columns:repeat(3,minmax(0,1fr));gap:12px;animation:.4s step-end arm;display:grid}.key{height:var(--key-h,64px);border:1px solid var(--key-border);border-bottom:4px solid var(--key-edge);border-radius:var(--radius-key);background:var(--key);color:var(--ink);justify-content:center;align-items:center;font-size:clamp(24px,4dvh,34px);font-weight:500;transition:transform 60ms ease-out,border-bottom-width 60ms ease-out;display:flex}.key:active{border-bottom-width:1px;transform:translateY(3px)}.key--quiet{color:var(--ink-soft)}.key--check{border-color:var(--mode-strong);border-bottom-color:var(--mode-ink);background:var(--mode-strong);color:#fff}.problem{font-variant-numeric:tabular-nums;color:var(--ink);font-size:clamp(32px,min(11cqi,11dvh),96px);font-weight:500;line-height:1.1}.problem--horizontal{flex-wrap:wrap;justify-content:center;align-items:center;gap:.3em;display:flex}.problem__op{color:var(--ink-soft)}.problem--stacked{grid-template-columns:auto auto;justify-content:center;column-gap:.3em;font-size:clamp(32px,min(16cqi,11dvh),96px);display:grid}.problem__top{text-align:right;grid-area:1/2}.problem__stack-op{grid-area:2/1}.problem__bottom{text-align:right;grid-area:2/2}.problem__rule{background:var(--ink);border-radius:999px;grid-area:3/1/auto/-1;height:.07em;margin:.12em 0 .18em}.problem__answer{grid-area:4/2;justify-content:flex-end;display:flex}.problem--stacked .digit{text-align:center;width:.64em;display:inline-block}.problem--stacked .problem__num{padding-right:.3em}.practice{--key-h:clamp(52px, 9dvh, 84px);padding-bottom:max(24px, calc(12px + env(safe-area-inset-bottom)))}@media (width>=700px) and (height>=600px){.practice{--key-h:clamp(64px, 9dvh, 84px)}}.back{height:44px;color:var(--ink-soft);background:0 0;border:none;border-radius:12px;align-items:center;gap:4px;padding:0 12px 0 6px;font-size:17px;display:inline-flex}@media (hover:hover){.back:hover{background:var(--hover)}}.back svg{font-size:22px}.practice__symbol{color:var(--mode-ink);font-size:28px;font-weight:600}.streak{background:var(--mode-fill);color:var(--mode-ink);white-space:nowrap;border-radius:999px;padding:4px 12px;font-size:15px;font-weight:500}.practice__body{flex:1;grid-template-rows:minmax(0,1fr) auto;gap:24px;min-height:0;display:grid}.practice__problem{justify-content:center;align-items:center;min-height:0;display:flex;container-type:inline-size}.practice__controls{width:100%;max-width:440px;min-height:calc(var(--key-h) * 4 + 36px);flex-direction:column;justify-content:center;margin:0 auto;display:flex}@media (orientation:landscape) and (width>=640px){.practice__body{grid-template-rows:minmax(0,1fr);grid-template-columns:minmax(0,1fr) min(420px,50%);align-items:center}}