checkbox.css

/* The container */
.container {
  display: block;
  position: relative;
  padding-left: 35px;
  margin-top: 4px;
  cursor: pointer;
  text-align: left;
  
  -webkit-user-select: none;
  -moz-user-select: none;
  -ms-user-select: none;
  user-select: none;
}

/* Hide the browser's default checkbox */
.container input {
  position: absolute;
  opacity: 0;
  cursor: pointer;
  height: 0;
  width: 0;
}

/* Create a custom checkbox */
.checkmark {
  position: absolute;
  top: 3;
  left: 3;
  height: 19px;
  width: 19px;
  background-color: #eee;
}

/* On mouse-over, add a grey background color */
.container:hover input ~ .checkmark {
  background-color: var(--shade-color);
}

/* When the checkbox is checked, add a gold background */
.container input:checked ~ .checkmark {
  background-color: var(--highlight-color);
}

/* Create the checkmark/indicator (hidden when not checked) */
.checkmark:after {
  content: "";
  position: absolute;
  display: none;
}

/* Show the checkmark when checked */
.container input:checked ~ .checkmark:after {
  display: block;
}

/* Style the checkmark/indicator */
.container .checkmark:after {
  left: 6px;
  top: 2px;
  width: 4px;
  height: 9px;
  border: solid var(--txt-color);
  border-width: 0 3px 3px 0;
  -webkit-transform: rotate(45deg);
  -ms-transform: rotate(45deg);
  transform: rotate(45deg);
}