estilos.css

* {
    margin: 0px;
    padding: 0px;
    font-size: 120%;
}

body {
    background: #171c26;
    height: calc(100vh - 10px);

    display: flex;
    align-items: center;
    justify-content: center;
}

.contenedor {
    background: #171c26;
    width: 100%;
    height: auto;

    margin-left: 1%;
    margin-right: 1%;

    display: grid;
    grid-template-columns: repeat(8, 1fr);
    grid-template-rows: repeat(2, 1fr);
    column-gap: 1%;
    row-gap: 4%;
}

.casilla {
    width: 100%;
    height: 0;
    padding-bottom: 100%;
    border-radius: 100%;

    position: relative;
    transform-style: preserve-3d;
    perspective: 1000px;
    display: flex;
    align-items: center;
    justify-content: center;
    transition: all 0.8s;
}

.tarjeta {
    width: 100%;
    height: 0;
    padding-bottom: 100%;
    grid-row: 2 / 3;
}
.btnaumen, .btndismi, .lblcontador {
    width: 100%;
    height: 0;
    padding-bottom: 100%;
    grid-row: 1 / 2;
}
.btnaumen {
    grid-column: 3 / 4;
    cursor: pointer;
}
.btndismi {
    grid-column: 6 / 7;
    cursor: pointer;
}
.lblcontador {
    grid-column: 4 / 6;
    left: 25%;
    width: 50%;
    height: 0;
    padding-bottom: 50%;
    font-size: 100%;
}

.apagado, .encendido {
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    
    position: absolute;
    backface-visibility: hidden;
    
    top: 0%;
    width: 100%;
    height: 100%;
    border-radius: 100%;
    background: #fdfffe;
    color: #171c26;
    border: 2px solid #4c5b7b;
}
.apagado {
    background: #171c26;
    color: #fdfffe;
    z-index: 2;
    transition: all 0.8s;
}
.encendido {
    transform: rotatex(180deg);
    transition: all 0.8s;
}

.aumen, .dismi, .contador {
    display: flex;
    align-items: center;
    justify-content: center;
    text-align: center;
    
    position: absolute;
    backface-visibility: hidden;
    
    top: 0%;
    width: 100%;
    height: 100%;
    border-radius: 100%;
    background: #fdfffe;
    color: #171c26;
    border: 2px solid #4c5b7b;
}