button {
 width: 140px;
 height: 45px;
 font-size: 23px;
 cursor: pointer;
 border: none;
 outline: none;
 background: transparent;
 color: white;
 font-family: 'Times New Roman', Times, serif;
 font-weight: 700;
 position: relative;
 transition: all 0.5s;
 z-index: 1;
}

button::before {
 content: "";
 position: absolute;
 top: 0;
 left: 0;
 width: 5px;
 height: 100%;
 background-color: white;
 z-index: -1;
 transition: all 0.5s;
}

button:hover::before {
 width: 100%;
}

button:hover {
 color: black;
}

button:active:before {
 background: #b9b9b9;
}