Download to Done

<button class="nuda-icon-download" type="button" aria-label="Download" aria-pressed="false">
  <svg class="nuda-icon-download__svg" viewBox="0 0 24 24" aria-hidden="true">
    <line class="nuda-icon-download__base" x1="5" y1="20" x2="19" y2="20" />
    <g class="nuda-icon-download__arrow">
      <line x1="12" y1="4" x2="12" y2="15" />
      <polyline points="7 11 12 16 17 11" />
    </g>
    <polyline class="nuda-icon-download__check" points="6 12 10 16 18 7" />
  </svg>
</button>

/* Download to Done
   Arrow drops away, baseline collapses, then a checkmark draws in.
   GPU-only: transform + opacity + dashoffset. Customize: --icon-accent */

.nuda-icon-download {
  --icon-accent: #e4ff54;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 44px;
  height: 44px;
  background: #09090b;
  border: 1px solid rgba(255, 255, 255, 0.1);
  border-radius: 10px;
  color: #fafafa;
  cursor: pointer;
  transition: border-color 0.25s, color 0.25s;
}

.nuda-icon-download:hover,
.nuda-icon-download:focus-visible {
  border-color: rgba(228, 255, 84, 0.4);
  outline: none;
}

.nuda-icon-download:focus-visible {
  box-shadow: 0 0 0 2px rgba(228, 255, 84, 0.5);
}

.nuda-icon-download[aria-pressed="true"] { color: var(--icon-accent); }

.nuda-icon-download__svg {
  width: 24px;
  height: 24px;
  stroke: currentColor;
  stroke-width: 2;
  stroke-linecap: round;
  stroke-linejoin: round;
  fill: none;
}

.nuda-icon-download__arrow,
.nuda-icon-download__base {
  transition: transform 0.35s cubic-bezier(0.4, 0.2, 0.2, 1), opacity 0.25s;
  transform-origin: center;
  will-change: transform, opacity;
}

.nuda-icon-download__check {
  stroke-dasharray: 24;
  stroke-dashoffset: 24;
  opacity: 0;
  transition: stroke-dashoffset 0.4s ease 0.15s, opacity 0.2s 0.15s;
}

.nuda-icon-download[aria-pressed="true"] .nuda-icon-download__arrow {
  opacity: 0;
  transform: translateY(8px) scale(0.6);
}

.nuda-icon-download[aria-pressed="true"] .nuda-icon-download__base {
  opacity: 0;
  transform: scaleX(0.4);
}

.nuda-icon-download[aria-pressed="true"] .nuda-icon-download__check {
  opacity: 1;
  stroke-dashoffset: 0;
}

@media (prefers-reduced-motion: reduce) {
  .nuda-icon-download__arrow,
  .nuda-icon-download__base,
  .nuda-icon-download__check { transition: opacity 0.25s; }
}

/* Download to Done — vanilla JS
   Marks pressed, shows the check, reverts after 1.8s. */

(function () {
  document.querySelectorAll(".nuda-icon-download").forEach(function (btn) {
    btn.addEventListener("click", function () {
      if (btn.getAttribute("aria-pressed") === "true") return;
      btn.setAttribute("aria-pressed", "true");
      btn.setAttribute("aria-label", "Downloaded");
      setTimeout(function () {
        btn.setAttribute("aria-pressed", "false");
        btn.setAttribute("aria-label", "Download");
      }, 1800);
    });
  });
})();