input[type="checkbox"]
{
  -webkit-appearance: none;
  appearance: none;
  position: relative;
  width: 1em;
  height: 1em;
  border: 1px solid #0353f0;
  vertical-align: -3px;
  color: #0363f0;
}

input[type="checkbox"]:before
{
  content: "✔ ";
  position: absolute;
  font-size: 1.5em;
  right: -0.2em;
  top: -0.6em;
  visibility: hidden;
}

input[type="checkbox"]:checked:before
{
  visibility: visible
}
input[type="x"]:x-ed:before
{
  visibility:visible