.change {
    perspective: 210px;
    padding-top: 60px;
    display: flex;
    align-items: center;
    justify-content: center;
    cursor: pointer;
}

.btn-change {

    --btn-height: 200px;
    --half-btn-height: calc(var(--btn-height) / 2);
    text-align: center;
    height: var(--btn-height);
    width: 320px;
    position: relative;
    transform-style: preserve-3d;
    transition: transform 0.8s ease-in-out;
    transform: translateZ(calc(-1 * var(--half-btn-height)));
}

.change .btn-change i {
    padding-right: 20px;
}

.btn-change:hover {
    transform: rotateX(-90deg) translateY(var(--half-btn-height));
}

.side {
    position: absolute;
    width: 100%;
    height: 100%;
    display: flex;
    justify-content: center;
    align-items: center;
    font-size: 40px;
    backface-visibility: hidden;
}

.default-side {

    background-color: var(--scarlet);
    color: var(--gold);
    transform: translateZ(var(--half-btn-height));

}

.hover-side {
    color: var(--scarlet);
    background-color: blue;
    transform: rotateX(90deg) translateZ(var(--half-btn-height));
}

.card-pdf {
    background-color: transparent;
    backdrop-filter: blur(25px);
    margin: 100px auto;
    border-radius: 20px;
    padding: 10px 20px;
    border: 2px;
    width: 300px;
    box-shadow: 10px 10px 20px black;
    transition: all 400ms ease-out;
    align-items: center;
}
@media screen and (min-width: 700px) {
    .card-pdf {
        width: 500px;
    }
}
.card-pdf:hover {
    border: 3px;
    box-shadow: 0px 35px 40px black;
    transform: translateY(-7%);
}
.card-pdf h1 {
    color: gainsboro;
    text-align: center;
    margin-bottom: 10px;
    margin-top: 5px;
    font-size: 26px;
}
.card-pdf h3 {
    color: var(--scarlet);
    margin-top: 30px;
    text-align: center;
    font-size: 23px;
}
.card-pdf h2 {
    color: rgb(0, 255, 0);
    font-size: 50px;
    text-align: center;
    margin-top: 125px;
}
.card-pdf h2:hover {
    color: blue;
    font-size: 70px;
    margin-top: 110px;
}
.send {
    border: 2px solid blue;
    cursor: pointer;
    background-color: blue;
    width: 260px;
    height: 340px;
    margin-top: 10px;
    margin-bottom: 20px;
    position: relative;
    display: inline-block;
    text-transform: uppercase;
    text-decoration: none;
    overflow: hidden;
    transition: 0.0010s;
}

@media screen and (min-width: 700px) {
    .send {
        width: 460px;
        margin-bottom: 40px;
    }
}

.send h3 {
    color: black;
    font-size: 40px;
    font-family: 'Exo', sans-serif;
}

@media(min-width: 700px) {
    .send h3 {
        font-size: 45px;
    }
}

.send:hover {

    background: rgb(0, 255, 0);
    box-shadow: 0 0 90px rgb(0, 255, 0),
        0 0 110px rgb(0, 255, 0),
        0 0 140px rgb(0, 255, 0);
    transition-delay: 0.7s;
}

@media screen and (min-width: 720px) {
    .send:hover {
        box-shadow: 0 0 120px rgb(0, 255, 0),
            0 0 150px rgb(0, 255, 0),
            0 0 190px rgb(0, 255, 0);

    }
}

.send:hover h3 {
    color: rgb(1, 102, 43);
    font-size: 60px;
}

@media(min-width: 700px) {
    .send:hover h3 {
        font-size: 70px;
    }
}

.send span {
    position: absolute;
    display: block;
}

.send span:nth-child(1) {
    top: 0;
    left: -100%;
    width: 100%;
    height: 360px;
    background: linear-gradient(90deg, transparent, rgb(0, 255, 0));
}

@media screen and (min-width: 700px) {
    .send span:nth-child(1) {
        height: 380px;
    }
}

.send:hover span:nth-child(1) {
    left: 100%;
    transition: 1s;
}

.send span:nth-child(2) {
    top: -100%;
    right: 0;
    width: 50px;
    height: 100%;
    background: linear-gradient(180deg, transparent, rgb(19, 255, 19));
}

.send:hover span:nth-child(2) {
    left: 100%;
    transition: 1s;
    transition-delay: 0.15s;
}

.send span:nth-child(3) {
    bottom: 0;
    right: -100%;
    width: 100%;
    height: 50px;
    background: linear-gradient(270deg, transparent, rgb(15, 253, 15));
}

.send:hover span:nth-child(3) {
    left: 100%;
    transition: 1s;
    transition-delay: 0.5s;
}

.send span:nth-child(4) {
    bottom: -100%;
    left: 0;
    width: 50px;
    height: 100%;
    background: linear-gradient(270deg, transparent, rgb(36, 255, 36));
}

.send:hover span:nth-child(4) {
    bottom: 100%;
    transition: 1s;
    transition-delay: 0.65s;
}