/* Block component */
.btn {
    width: 50px;
    background-color: blue;
    padding: 0.5rem;
}

/* Element depends upon block */
.btn__price {
    font-size: 0.6rem;
}

/* Modifier changes style of block */
.btn--orange {
    background-color: orange;
}

.btn--big {
    width: 75px;
    padding: 1rem;
}