.button-round {
    width: 88px;
    height: 88px;
    border-radius: 50%;
    display: flex;
    justify-content: center;
    align-items: center;
    transition: transform 300ms ease;
}

.button-round.small {
    width: 45px;
    height: 45px;
}

.button-round:hover {
    background-color: white;
    box-shadow: inset 0 0 0 1px var(--yellow);
}

.button-play, .button-expand {
    background-color: var(--yellow);
}

.button-close {
    background-color: var(--grey);
}

.button-play span {
    display: inline-block;
    box-sizing: border-box;
    position:relative;
    left: 6px;
    width: 30px;
    height: 30px;
    border-style: solid;
    border-color: transparent transparent transparent black;
    border-width: 15px 0 15px 30px;
}