* {
    box-sizing: border-box;
    margin: 0;
    font-family: system-ui, sans-serif;
}
span, a, label {
    display: inline-block;
}
img {
    max-width: 100%;
    height: auto;
    vertical-align: middle;
}
.box {
    min-height: 100dvh;
    background-color: #eee;
    padding: 100px;
    display: flex;
    flex-direction: column;
    flex-wrap: wrap;
    justify-content: center;
    align-items: flex-start;
    row-gap: 30px;
}
.btn {
    font-size: 40px;
    width: 420px;
    height: 130px;
    text-transform: uppercase;
    background-color: transparent;
    cursor: pointer;
    z-index: 1;
    transition: 0.4s;
    position: relative;
}
.btn:hover {
    color: white;
}
.btn1 {
    border: 3px solid teal;
    color: teal;
}
.part {
    position: absolute;
    width: 25%;
    height: 0;
    background-color: teal;
    transition: 0.4s;
    z-index: -1;
}
.part1, .part3 {
    top: 0;
}
.part2, .part4 {
    bottom: 0;
}
.part1 {
    left: 0;
}
.part2 {
    left: 25%;
}
.part3 {
    right: 25%;
}
.part4 {
    right: 0;
}
.btn1:hover .part {
    height: 100%;
}
.btn2 {
    border: 3px solid forestgreen;
    color: forestgreen;
}
.btn2::before, .btn2::after {
    content: '';
    position: absolute;
    width: 100%;
    height: 0;
    left: 0;
    transition: 0.4s;
    z-index: -1;
}
.btn2::before {
    top: 0;
    background-color: forestgreen;
}
.btn2::after {
    bottom: 0;
    background-color: forestgreen;
}
.btn2:hover::before, .btn2:hover::after {
    height: 50%;
}