The $900 million checkbox   

<!-- Hold-to-confirm checkbox · metic.studio · Million-Dollar Details EP 02 -->
<button class="hold-check" type="button" role="checkbox" aria-checked="false">
  <span class="hold-check__box">
    <svg viewBox="0 0 30 30" aria-hidden="true">
      <path class="hold-check__edge" pathLength="1"
        d="M15 .75H21A8.25 8.25 0 0 1 29.25 9V21A8.25 8.25 0 0 1 21 29.25H9A8.25 8.25 0 0 1 .75 21V9A8.25 8.25 0 0 1 9 .75Z"/>
      <circle class="hold-check__dot" cx="9" cy="15.5" r="3.4"/>
      <path class="hold-check__tick" pathLength="1" d="M9 15.5L13.3 19.8 21.5 10.5"/>
    </svg>
  </span>
  <span>Pay off the whole loan<small>hold to confirm</small></span>
</button>

<style>
  .hold-check {
    --ink: #121214; --line: rgb(18 18 20 / .32); --accent: #ff3e3e; --lens: cubic-bezier(.23, 1, .32, 1);
    all: unset; display: inline-flex; align-items: center; gap: 14px; min-height: 48px; cursor: pointer;
    font: 500 17px/1.25 system-ui, sans-serif; -webkit-tap-highlight-color: transparent; touch-action: manipulation;
  }
  .hold-check small { display: block; font: 12.5px ui-monospace, monospace; color: var(--accent); }
  .hold-check__box {
    position: relative; width: 30px; height: 30px; box-sizing: border-box; border: 1.5px solid var(--line); border-radius: 9px;
    transition: border-color .3s var(--lens) .1s, transform .16s var(--lens);
  }
  .hold-check__box svg { position: absolute; inset: -1.5px; width: 30px; height: 30px; overflow: visible; }
  /* the border fills while you hold */
  .hold-check__edge { fill: none; stroke: var(--accent); stroke-width: 2.6; stroke-linecap: round;
    stroke-dasharray: 1; stroke-dashoffset: 1; transition: opacity .35s var(--lens) .2s; }
  .hold-check__tick { fill: none; stroke: var(--accent); stroke-width: 2.8; stroke-linecap: round; stroke-linejoin: round;
    stroke-dasharray: 1; stroke-dashoffset: 1; transition: stroke-dashoffset .22s ease-in; }
  .hold-check__dot { fill: var(--accent); transform-box: fill-box; transform-origin: center; transform: translateY(-22px) scale(0); }
  .hold-check.is-holding .hold-check__box { transform: scale(.96); }
  /* confirmed: the red dot drops in and becomes the check */
  .hold-check[aria-checked="true"] .hold-check__box { border-color: var(--ink); }
  .hold-check[aria-checked="true"] .hold-check__edge { opacity: 0; }
  .hold-check[aria-checked="true"] .hold-check__dot { animation: hold-check-drop .5s var(--lens) .08s forwards; }
  .hold-check[aria-checked="true"] .hold-check__tick { stroke-dashoffset: 0; transition: stroke-dashoffset .32s var(--lens) .28s; }
  .hold-check.is-shaking .hold-check__box { animation: hold-check-shake .32s var(--lens); }
  .hold-check:focus-visible .hold-check__box { outline: 2px solid var(--accent); outline-offset: 3px; }
  @keyframes hold-check-drop {
    0% { transform: translateY(-22px) scale(1); }
    32% { transform: translateY(0) scale(1.15, .8); }
    45% { transform: translateY(0) scale(1); }
    100% { transform: translateY(0) scale(0); }
  }
  @keyframes hold-check-shake { 25% { transform: translateX(-3px); } 60% { transform: translateX(2px); } }
  @media (prefers-reduced-motion: reduce) { .hold-check * { transition-duration: .01ms !important; animation-duration: .01ms !important; } }
</style>

<script>
  // Hold 900 ms to confirm. Let go early and the border runs back. One click unchecks.
  document.querySelectorAll('.hold-check').forEach((btn) => {
    const edge = btn.querySelector('.hold-check__edge'), HOLD = 900
    let t0 = 0, p = 0, raf = 0, holding = false
    const set = (v) => (edge.style.strokeDashoffset = 1 - v)
    const check = (on) => btn.setAttribute('aria-checked', String(on))
    const frame = (now) => {
      if (!holding) return
      p = Math.min(1, (now - t0) / HOLD); set(p)
      if (p === 1) { holding = false; btn.classList.remove('is-holding'); check(true); setTimeout(() => set(0), 700); return }
      raf = requestAnimationFrame(frame)
    }
    const start = () => {
      if (btn.getAttribute('aria-checked') === 'true') return check(false)
      holding = true; t0 = performance.now(); btn.classList.add('is-holding'); raf = requestAnimationFrame(frame)
    }
    const stop = () => {
      if (!holding) return
      holding = false; cancelAnimationFrame(raf); btn.classList.remove('is-holding')
      btn.classList.remove('is-shaking'); void btn.offsetWidth; btn.classList.add('is-shaking')
      const from = p, s = performance.now()
      const back = (now) => { const q = Math.min(1, (now - s) / 320); set(from * Math.pow(1 - q, 3)); if (q < 1) requestAnimationFrame(back) }
      requestAnimationFrame(back)
    }
    btn.addEventListener('pointerdown', (e) => { e.preventDefault(); start() })
    ;['pointerup', 'pointerleave', 'pointercancel'].forEach((ev) => btn.addEventListener(ev, stop))
    btn.addEventListener('keydown', (e) => { if ((e.key === ' ' || e.key === 'Enter') && !e.repeat) { e.preventDefault(); start() } })
    btn.addEventListener('keyup', (e) => { if (e.key === ' ' || e.key === 'Enter') stop() })
  })
</script>