*{box-sizing:border-box;-webkit-tap-highlight-color:transparent}body{margin:0;background:#fff;color:#000;font-family:'Yu Gothic',sans-serif}main{max-width:420px;min-height:640px;height:100svh;margin:auto;padding:48px 16px 24px;position:relative}h1{font:500 28px 'Yu Mincho',serif;letter-spacing:.12em;text-align:center;margin:0}.equation{user-select:none;-webkit-user-select:none;-webkit-tap-highlight-color:transparent;margin:96px auto 0;width:max-content;max-width:100%;font:clamp(23px,7.5vw,27px)/1.3 'Cambria Math',serif;white-space:nowrap}.row{display:flex;align-items:center;justify-content:center;height:64px}.part{display:inline-block;position:relative;cursor:pointer;touch-action:manipulation;outline:none}.term{padding:2px}.op{padding:2px 5px}.product{padding:7px 2px}.sum{padding:4px 0}.inside{display:inline-block;padding:4px 2px;border-radius:3px}i{font-family:Cambria,'Times New Roman',serif}sup{font-size:.6em;line-height:0;position:relative;top:-.15em}.selected{background:#dcecf8;border-radius:3px}.part:focus-visible{outline:1px dashed #333;outline-offset:2px}.choices{height:54px;margin-top:35px;display:flex;gap:16px;align-items:center;justify-content:center}button{font:inherit;color:inherit;background:none;border:none;cursor:pointer;touch-action:manipulation}button:focus-visible{outline:2px solid #56758b;outline-offset:3px}.choice{width:44px;height:44px;display:grid;place-items:center;padding:0}.circle{display:block;width:24px;height:24px;border:1.4px solid #000;border-radius:50%}.slots{display:flex;justify-content:center;gap:10px;margin-top:36px}.slot{width:43px;height:47px;border:1px solid #848484;position:relative;display:grid;place-items:center}.slot:nth-child(4):after{content:'';position:absolute;right:5px;top:5px;width:9px;height:8px;background:no-repeat center/contain url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 9 8'%3E%3Cpath d='M1 2L3 5M5 1L7 4' fill='none' stroke='black' stroke-width='1.5' stroke-linecap='round'/%3E%3C/svg%3E");pointer-events:none}.erase{display:block;margin:18px auto 0;padding:10px;font-size:13px;color:#999}.restart{display:block;position:absolute;bottom:18px;left:50%;transform:translateX(-50%);padding:10px;font-size:12px;color:#666}@media(max-height:640px){main{padding-top:28px;min-height:560px}.equation{margin-top:65px}.choices{margin-top:20px}.slots{margin-top:24px}}

#b,#d{display:inline-block}.dot{width:9px;height:9px;background:#000;border-radius:50%}.erase:not(:disabled){color:#444}button:disabled{cursor:default}.choice:disabled{opacity:.3}.wrong{animation:shake .25s} @keyframes shake{25%,75%{transform:translateX(-4px)}50%{transform:translateX(4px)}}@media(prefers-reduced-motion:reduce){.wrong{animation:none;outline:1px solid #666}}dialog{border:0;padding:38px 30px;width:min(304px,90vw);text-align:center}dialog::backdrop{background:#0003}dialog .title{font:20px 'Yu Mincho',serif;margin:0 0 22px}dialog h2{font-size:25px;font-weight:500}dialog .answer{font:25px 'Yu Mincho',serif;margin:24px 0 30px}dialog button{padding:12px 20px}.reopen{display:block;margin:12px auto;font-size:12px}[hidden]{display:none!important}
.answer-slots{display:flex;justify-content:center;gap:6px;margin:26px 0 30px}.answer-slot{display:grid;place-items:center;width:43px;height:47px;flex:none;border:1px solid #848484;font:25px/1 "Yu Mincho",serif}dialog{padding-left:20px;padding-right:20px}

:root{--background:#fff;--surface:#fff;--ink:#000;--accent:#000;--on-accent:#fff;--border:#848484;--muted:#666;--radius:0;font-family:"Yu Gothic",sans-serif}main{text-align:initial}main button{min-height:44px;border-radius:0}.erase,.restart{border:0;background:none}.choice{border:0;min-height:44px}#restart{margin:0}.reopen{border:0;background:none;min-height:44px}.part:focus-visible{outline-offset:2px}#clear-dialog{width:304px;max-width:calc(100% - 24px);padding:38px 20px 26px;border:0}#clear-dialog h2{font:500 25px/1.5 "Yu Gothic",sans-serif;margin:0 0 24px}#clear-result{margin:0}.answer-slots{margin:0 0 26px}#share{width:100%;margin:0 0 12px;font-size:14px;padding:12px}#return{border:0;margin:0 auto;padding:10px 20px;font-size:14px}.clear-links{font-size:11px;gap:10px;margin-top:22px}#close-clear{padding:8px;min-height:36px}.slots.wrong{pointer-events:none}

.bottom-product{display:inline-flex;align-items:center;padding:7px 2px}

#sound{position:absolute;top:8px;right:12px;display:grid;place-items:center;width:44px;height:44px;min-height:44px;padding:10px;border:0;background:transparent;color:#555;border-radius:0}
#sound svg{width:24px;height:24px;fill:none;stroke:currentColor;stroke-width:1.6;stroke-linecap:round;stroke-linejoin:round}
#sound[aria-checked="false"] .sound-on,#sound[aria-checked="true"] .sound-off{display:none}