nelle-observer/public/styles/css/nav-buttons.css

.custom-btn {
    width: 130px;
    height: 40px;
    color: --text;
    border-radius: 5px;
    padding: 10px 25px;
    font-weight: 500;
    background: transparent;
    cursor: pointer;
    transition: all 0.3s ease;
    position: relative;
    display: inline-block;
    box-shadow: inset 2px 2px 2px 0px rgba(255, 255, 255, .5),
        7px 7px 20px 0px rgba(0, 0, 0, .1),
        4px 4px 5px 0px rgba(0, 0, 0, .1);
    outline: none;
    font-size: large;
    -webkit-box-shadow: 0 0 10px var(--accent);
    -moz-box-shadow: 0 0 10px var(--accent);
    box-shadow: 0 0 10px var(--accent);
}

/* 8 */
.btn-1 {
    background-color: var(--background);
    background-image: linear-gradient(315deg, var(--text) 0%, var(--accent) 74%);
    line-height: 42px;
    padding: 0;
    border: none;
}

.btn-1 span {
    position: relative;
    display: block;
    width: 100%;
    height: 100%;
}

.btn-1:before,
.btn-1:after {
    position: absolute;
    content: "";
    right: 0;
    bottom: 0;
    background: var(--accent);
    /*box-shadow:  4px 4px 6px 0 rgba(255,255,255,.5),
                -4px -4px 6px 0 rgba(116, 125, 136, .2), 
      inset -4px -4px 6px 0 rgba(255,255,255,.5),
      inset 4px 4px 6px 0 rgba(116, 125, 136, .3);*/
    transition: all 0.3s ease;
}

.btn-1:before {
    height: 0%;
    width: 2px;
}

.btn-1:after {
    width: 0%;
    height: 2px;
}

.btn-1:hover:before {
    height: 100%;
}

.btn-1:hover:after {
    width: 100%;
}

.btn-1:hover {
    background: transparent;
}

.btn-1 span:hover {
    color: var(--accent);
}

.btn-1 span:before,
.btn-1 span:after {
    position: absolute;
    content: "";
    left: 0;
    top: 0;
    background: var(--accent);
    /*box-shadow:  4px 4px 6px 0 rgba(255,255,255,.5),
                -4px -4px 6px 0 rgba(116, 125, 136, .2), 
      inset -4px -4px 6px 0 rgba(255,255,255,.5),
      inset 4px 4px 6px 0 rgba(116, 125, 136, .3);*/
    transition: all 0.3s ease;
}

.btn-1 span:before {
    width: 2px;
    height: 0%;
}

.btn-1 span:after {
    height: 2px;
    width: 0%;
}

.btn-1 span:hover:before {
    height: 100%;
}

.btn-1 span:hover:after {
    width: 100%;
}