광고 수익률 (ROAS)

<div class="calc"><div class="head">REVENUE <strong>$400</strong></div><label for="spend">AD SPEND <output id="amount">$100</output></label><input id="spend" type="range" min="50" max="300" step="10" value="100"><div class="result"><span>ROAS</span><b id="roas">4.0×</b></div></div>

.calc{width:min(85%,440px);background:var(--surface);border:1px solid var(--line);padding:clamp(14px,4vmin,34px);box-shadow:7px 7px 0 var(--line);font:800 clamp(10px,2vmin,16px)/1.2 sans-serif}.head,.calc label{display:flex;justify-content:space-between;align-items:center;letter-spacing:.05em}.head{color:var(--muted);margin-bottom:clamp(10px,3vmin,26px)}.head strong{color:var(--fg);font-size:clamp(15px,3vmin,24px)}.calc label output{color:var(--accent)}input{width:100%;margin:clamp(11px,2.5vmin,22px) 0;accent-color:var(--accent);cursor:pointer}.result{border-top:2px solid var(--fg);padding-top:clamp(8px,2vmin,18px);display:flex;align-items:center;justify-content:space-between}.result b{font-size:clamp(32px,9vmin,78px);color:var(--accent);letter-spacing:-.08em}

const input=document.querySelector('#spend'),amount=document.querySelector('#amount'),roas=document.querySelector('#roas');function update(){amount.textContent='$'+input.value;roas.textContent=(400/Number(input.value)).toFixed(1)+'×'}input.addEventListener('input',update);let v=100,step=10;const timer=setInterval(()=>{if(document.activeElement===input){clearInterval(timer);return}v+=step;if(v>=250||v<=80)step*=-1;input.value=String(v);update()},650);