checkbox.css

/* Notation checkboxes */
.markdown-preview-view .task-list-item-checkbox {
  -webkit-appearance: none;
  box-sizing: border-box;
  border: 1px solid var(--text-normal);
  position: relative;
  width: 16px;
  height: 16px;
  margin: 0;
  margin-right: 4px;
  margin-bottom: 2px;
  transition: background-color 200ms ease-out 0s;
  cursor: pointer;
  filter: none;
  border-radius: 4px;
}

.markdown-preview-view .task-list-item-checkbox:checked {
  border: none;
  background-color: var(--interactive-accent);
}

.markdown-preview-view .task-list-item-checkbox:hover {
  background-color: var(--background-primary-alt);
}

.markdown-preview-view .task-list-item-checkbox:checked::before {
  position: absolute;
  color: white;
  text-align: center;
  font-weight: 900;
  line-height: 15px;
  width:12px;
  left:2px;
  right:2px;
}

.markdown-preview-view ul>li.task-list-item {
  font-weight: normal;
  color: var(--text-normal);
}

/* SVG check mark for done ('- [x]') */
.markdown-preview-view li[data-task="x"]>.task-list-item-checkbox:checked::before,
.markdown-preview-view li[data-task="X"]>.task-list-item-checkbox:checked::before {
  content: ' ';
  top: 2px;
  bottom: 2px;
  background-color: white;
  -webkit-mask-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' viewBox='0 0 14 14'%3E%3Cpolygon points='5.5 11.9993304 14 3.49933039 12.5 2 5.5 8.99933039 1.5 4.9968652 0 6.49933039'%3E%3C/polygon%3E%3C/svg%3E");
}

/* SVG chevron right for deferred/scheduled ('- [>]') */
.markdown-preview-view li[data-task=">"]>.task-list-item-checkbox:checked::before {
  content: '';
  top:2px;
  bottom:2px;
  background-color: white;
  -webkit-mask-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 14 14' xmlns='http://www.w3.org/2000/svg'%3E%3Cpath d='M8.12 7L3.26667 11.76L4.57333 13.0667L10.7333 7L4.57333 0.933332L3.26667 2.24L8.12 7Z'/%3E%3C/svg%3E");
}

/* SVG line for cancelled/non-task ('- [-]') */
.markdown-preview-view li[data-task="-"]>.task-list-item-checkbox:checked::before {
  content: '';
  top:2px;
  bottom:2px;
  background-color: white;
  -webkit-mask-image: url("data:image/svg+xml,%3Csvg viewBox='0 0 14 14' xmlns='http://www.w3.org/2000/svg'%3E%3Crect x='0.5' y='6.5' width='13' height='1'/%3E%3C/svg%3E");
}
/* greyed-out background colour for cancelled/non-task ('- [-]') */
.markdown-preview-view li[data-task="-"]>.task-list-item-checkbox:checked {
  background-color: var(--text-faint);
}

/* '?' for question/more info task ('- [?]') */
.markdown-preview-view li[data-task="?"]>.task-list-item-checkbox:checked::before {
  content: '?';
}
/* text style for question/more info task ('- [?]') */
.markdown-preview-view ul>li[data-task="?"].task-list-item.is-checked {
  color: var(--text-normal);
  text-decoration: none;
}
/* yellow background colour for question/more info task ('- [?]') */
.markdown-preview-view li[data-task="?"]>.task-list-item-checkbox:checked{
  background-color: #A99400;
}

/* '!' for important task ('- [!]') */
.markdown-preview-view li[data-task="!"]>.task-list-item-checkbox:checked::before {
  content: '!';
}
/* text style for important task ('- [!]') */
.markdown-preview-view ul>li[data-task="!"].task-list-item.is-checked {
  color: var(--text-normal);
  text-decoration: none;
  font-weight: 900;
}
/* red background colour for important task ('- [!]') */
.markdown-preview-view li[data-task="!"]>.task-list-item-checkbox:checked {
  background-color: #a90000;
}