button css

html,
body,
.checkbox,
.checkbox .inner,
.checkbox .inner .toggle {
    height: 100%;
    display: flex;
    align-items: center;
    justify-content: center;
}

.checkbox {
    width: 10em;
    height: 5em;
    background: linear-gradient(silver, whitesmoke);
    border-radius: 2.5em;
    font-size: 30px;
}

.checkbox .inner {
    width: 8em;
    height: 3.5em;
    background: linear-gradient(dimgray, silver);
    border-radius: 2em;
    box-shadow: inset 0 0 1.5em rgba(0, 0, 0, 0.5);
}

.checkbox .inner .toggle {
    width: 3.5em;
    height: 3.5em;
    background: linear-gradient(to top, silver, whitesmoke);
    border-radius: 50%;
    box-shadow: 0 0.4em 0.6em rgba(0, 0, 0, 0.2);
    position: relative;
    left: -30%;
    transition: 0.5s;
}

.checkbox .inner .toggle::before {
    content: 'OFF';
    position: absolute;
    width: 80%;
    height: 80%;
    background: linear-gradient(silver, whitesmoke);
    border-radius: 50%;
    text-align: center;
    line-height: calc(3.5em * 0.8);
    font-family: sans-serif;
    color: gray;
}

.checkbox .inner.active {
    background: linear-gradient(green, limegreen);
}

.checkbox .inner.active .toggle {
    left: 30%;
}

.checkbox .inner.active .toggle::before {
    content: 'ON';
    color: limegreen;
}