.cube .sticker {
    position: relative;
}

.cube .sticker::before {
    position: absolute;
    content: '';
    top: 0px;
    left: 0px;
    width: 100%;
    height: 100%;
    box-sizing: border-box;
    border: solid 8px #0a0a0a;
    /* Previous value => solid 6px #0a0a0a; */
    border-radius: 16px;
}

.cube .sticker::after {
    position: absolute;
    content: '';
    top: -1px;
    left: -1px;
    width: calc(100% + 2px);
    height: calc(100% + 2px);
    box-sizing: border-box;
    border: solid 8px #0a0a0a;
    /* Previous value => solid 7px #0a0a0a; */
}