Cherchez le rayon de la bordure cochée CSS
<style>
.checkbox-round {
width: 1.3em;
height: 1.3em;
background-color: white;
border-radius: 50%;
vertical-align: middle;
border: 1px solid #ddd;
appearance: none;
-webkit-appearance: none;
outline: none;
cursor: pointer;
}
.checkbox-round:checked {
background-color: gray;
}
</style>
<input type="checkbox" class="checkbox-round" />
<demo>
https://jsfiddle.net/287a4boL
</demo>
Mr. Codex