style.css

* {
    padding: 0;
    margin: 0;
    box-sizing: border-box;
    font-family: sans-serif;
}

body {
    display: flex;
    justify-content: center;
    align-items: center;
    width: 100%;
    height: 100vh;
    background: #1a1a1a;
    
}

.btn {
    display: block;
    text-decoration: none;
    text-transform: uppercase;

    font-size: 11px;
    font-weight: bold;
    color: #fff;

    margin: 0 15px;
    padding: 10px 35px;

    border: 2px solid #5fe36a;

    overflow: hidden;

    position: relative;

}

.btn::before {
    content: "";
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%,-50%);

    width: 100%;
    height: 100%;

    background-color: #5fe36a;

    z-index: -1;

    transition: .7s ease;

}

/* ----------------- btn1 ----------------- */

.btn1::before {
    width: 0;
    height: 100%;
}

.btn1:hover::before {
    width: 110%;
}

/* ----------------- btn2 ----------------- */

.btn2::before {
    width: 110%;
    height: 0;
}

.btn2:hover::before {
    height: 110%;
}

/* ----------------- btn3 ----------------- */

.btn3::before {
    width: 110%;
    height: 0;
    transform: translate(-50%,-50%) rotate(45deg);
}

.btn3:hover::before {
    height: 350%;
}

/* ----------------- btn4 ----------------- */

.btn4::before {
    width: 110%;
    height: 0;
    transform: translate(-50%,-50%) rotate(-45deg);
}

.btn4:hover::before {
    height: 350%;
}

/* ----------------- btn5 ----------------- */

.btn5::before {
    width: 110%;
    height: 0;
    border-radius: 50%;
}

.btn5:hover::before {
    height: 350%;
}

/* ----------------- responsivo ----------------- */

@media(max-width: 700px) {

    body {
        flex-direction: column;
    }

    .btn {
        margin: 20px 15px;
        padding: 10px 35px;
    }


}