buttonSelected style css

* {
    margin: 0;
    padding: 0;
    box-sizing: border-box;
}

body {
    width: 100vw;
    height: 100vh;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: center;
    flex-wrap: nowrap;
}

.titulo {
    width: 100%;
    height: 200px;
    display: flex;
    flex-direction: row;
    justify-content: center;
    align-items: center;
    flex-wrap: nowrap;
}

.contenedor--botones {
    width: 600px;
    height: 100%;
    display: flex;
    flex-direction: column;
    justify-content: flex-start;
    align-items: flex-start;
    flex-wrap: nowrap;
}

.filas {
    width: 100%;
    height: 100px;
    display: flex;
    flex-direction: row;
    justify-content: space-evenly;
    align-items: center;
    flex-wrap: nowrap;
}

.boton {
    height: 80px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    align-items: center;
    flex-wrap: nowrap;
    flex-grow: 1;
    margin-left: 20px;
    font-size: 34px;
    font-weight: bold;
    cursor: pointer;
    border: 1px solid black;
    border-radius: 20px;
    transition: 0.3s;
}

.boton:hover {
    color: #fff;
    background-color: rgb(51, 51, 51);
    transition: 0.3s;
}

.boton:nth-child(3) {
    margin-right: 20px;
}

.boton-disabled {
    border-color: rgb(119, 119, 119);
    color: rgb(119, 119, 119);
    pointer-events: none;
}