button.css

.container {
    display: flex;
    justify-content: center;
    align-items: center;
    align-content: center;
    flex-wrap: wrap;
    width: 60vw;
    max-width: 1200px;
    margin: 0 auto;
    min-height: 10vh;
}
.button {
    flex: 1 1 auto;
    margin: 10px;
    padding: 15px;
    border: 2px solid #f7f7f7;
    text-align: center;
    text-transform: uppercase;
    position: relative;
    overflow: hidden;
    transition: 0.3s;
    font-family: cursive;
    font-weight: bold;
}
.button:after {
    position: absolute;
    transition: 0.3s;
    content: '';
    width: 0;
    left: 50%;
    bottom: 0;
    height: 3px;
    background: #f7f7f7;
    height: 120%;
    left: -10%;
    transform: skewX(15deg);
    z-index: -1;
}
.button:hover {
    cursor: pointer;
    color: #5bcaff;
}
.button:hover:after {
    width: 100%;
    left: 0;
    left: -10%;
    width: 120%;
}