Zöld harmonika

.we-btn-fold {
    position: relative;

    display: inline-flex;
    align-items: center;
    justify-content: center;
    gap: 16px;

    min-width: 185px;
    height: 54px;

    padding: 0 27px;

    border: 1px solid rgba(63,159,99,.3);
    border-radius: 13px;

    background: #101713;
    color: #f1f3ee;

    font-family: Arial, sans-serif;
    font-size: 14px;
    font-weight: 500;
    letter-spacing: .4px;

    cursor: pointer;
    overflow: hidden;

    perspective: 500px;

    transition:
        transform .8s cubic-bezier(.22,1,.36,1),
        border-radius .8s ease,
        box-shadow .8s ease;
}

.we-btn-fold-left,
.we-btn-fold-right {
    position: absolute;

    top: 0;

    width: 51%;
    height: 100%;

    background: #3f9f63;

    transition:
        transform 1.05s cubic-bezier(.22,1,.36,1),
        border-radius 1s ease;
}

.we-btn-fold-left {
    left: 0;

    transform-origin: left center;
    transform: perspective(500px) rotateY(0deg);
}

.we-btn-fold-right {
    right: 0;

    transform-origin: right center;
    transform: perspective(500px) rotateY(0deg);
}

.we-btn-fold-text,
.we-btn-fold-arrow {
    position: relative;
    z-index: 3;

    transition:
        transform .9s cubic-bezier(.22,1,.36,1),
        color .6s ease;
}

.we-btn-fold-arrow {
    font-size: 20px;
}

.we-btn-fold:hover {
    transform:
        translateY(-5px);

    border-radius: 18px;

    box-shadow:
        0 24px 46px rgba(0,0,0,.44);
}

.we-btn-fold:hover .we-btn-fold-left {
    transform:
        perspective(500px)
        rotateY(72deg)
        translateX(-5px);
}

.we-btn-fold:hover .we-btn-fold-right {
    transform:
        perspective(500px)
        rotateY(-72deg)
        translateX(5px);
}

.we-btn-fold:hover .we-btn-fold-text {
    color: #8ac99b;

    transform:
        translateX(-4px);
}

.we-btn-fold:hover .we-btn-fold-arrow {
    color: #5fbd7d;

    transform:
        translateX(8px)
        scale(1.12);
}

.we-btn-fold:active {
    transform:
        translateY(-1px)
        scale(.97);
}

Ehhez az animációhoz nincs külön JavaScript.