全屏

<span class="open-icon-full"></span>

<style>

.open-icon-full{
    display: inline-block;
    position: relative;
    width: 12px;
    height: 12px;
    border-radius: var(--radius-box);
    border: 1px solid var(--color-font-1);
    transition: all .5s;
}
.open-icon-full::before{
    content: '';
    position: absolute;
    top: -3px;
    right: -3px;
    width: 10px;
    height: 10px;
    border-radius: var(--radius-box);
    border-top: 1px solid var(--color-font-1);
    border-right: 1px solid var(--color-font-1);
    transition: all .5s;
}
.open-icon-full:hover,.open-icon-full:hover::before{
    border-color: var(--app-color-2);
}

</style>