Dart animation forwards fill mode

fadeout.dart

import 'dart:html';

void main() {
  var el = Element.div();
  el.style.backgroundColor = "#881003";
  el.text = "HELLO WORLD";
  el.style.width = "400px";
  el.style.height = "400px";
  document.body.append(el);
  
  el.onClick.listen((_) {
    el.text = "OH NO! I'M FADING AWAY";
    el.animate([{"opacity": 0}], {
      "duration": 1000,
      "fill": "forwards"
    });
  });
}