forgejo/web_src/css/modules/checkbox.css

/* based on Fomantic UI checkbox module, with just the parts extracted that we use. If you find any
   unused rules here after refactoring, please remove them. */

input[type="checkbox"],
input[type="radio"] {
  width: var(--checkbox-size);
  height: var(--checkbox-size);
}

.ui.checkbox {
  position: relative;
  display: inline-block;
  vertical-align: baseline;
  min-height: var(--checkbox-size);
  line-height: var(--checkbox-size);
  min-width: var(--checkbox-size);
  padding: 1px;
}

.ui.checkbox input[type="checkbox"],
.ui.checkbox input[type="radio"] {
  position: absolute;
  top: 1px;
  left: 0;
  width: var(--checkbox-size);
  height: var(--checkbox-size);
}

.ui.checkbox input[type="checkbox"]:enabled,
.ui.checkbox input[type="radio"]:enabled,
.ui.checkbox label:enabled {
  cursor: pointer;
}

.ui.checkbox label {
  cursor: auto;
  position: relative;
  display: block;
  user-select: none;
}

.ui.checkbox label,
.ui.radio.checkbox label {
  margin-left: 1.85714em;
}

.ui.checkbox + label {
  vertical-align: middle;
}

.ui.disabled.checkbox label,
.ui.checkbox input[disabled] ~ label {
  cursor: default !important;
  opacity: 0.5;
  pointer-events: none;
}

.ui.radio.checkbox {
  min-height: var(--checkbox-size);
}

/* "switch" styled checkbox */

.ui.toggle.checkbox {
  min-height: 1.5rem;
}
.ui.toggle.checkbox input {
  width: 3.5rem;
  height: 1.5rem;
  opacity: 0;
  z-index: 3;
}
.ui.toggle.checkbox label {
  min-height: 1.5rem;
  padding-left: 4.5rem;
  padding-top: 0.15em;
}
.ui.toggle.checkbox label::before {
  display: block;
  position: absolute;
  content: "";
  z-index: 1;
  top: 0;
  width: 3.5rem;
  height: 1.5rem;
  border-radius: 500rem;
  left: 0;
}
.ui.toggle.checkbox label::after {
  background: var(--color-white);
  position: absolute;
  content: "";
  opacity: 1;
  z-index: 2;
  width: 1.5rem;
  height: 1.5rem;
  top: 0;
  left: 0;
  border-radius: 500rem;
  transition: background 0.3s ease, left 0.3s ease;
}
.ui.toggle.checkbox input ~ label::after {
  left: -0.05rem;
}
.ui.toggle.checkbox input:checked ~ label::after {
  left: 2.15rem;
}
.ui.toggle.checkbox input:focus ~ label::before,
.ui.toggle.checkbox label::before {
  background: var(--color-input-toggle-background);
}
.ui.toggle.checkbox label,
.ui.toggle.checkbox input:checked ~ label,
.ui.toggle.checkbox input:focus:checked ~ label {
  color: var(--color-text) !important;
}
.ui.toggle.checkbox input:checked ~ label::before,
.ui.toggle.checkbox input:focus:checked ~ label::before {
  background: var(--color-primary) !important;
}