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

body {
    display: flex;
    justify-content: center;
    align-items: center;
    /* isso faz com que fique sempre no centro */
    min-height: 100vh; 
    /* --------------------------------------- */
    flex-direction: column;
    background: #2b2b2b;
}

label {
    position: relative;
    margin: 5px 0;
    cursor: pointer;
}

label input {
    appearance: none;
    display: none;
}

label span {
    position: relative;
    display: block;
    width: 80px;
    height: 40px;
    background: #222;
    border-radius: 40px;
    box-shadow: inset 0 2px 15px rgba(0, 0, 0, 0.2),
                inset 0 2px 15px rgba(0, 0, 0, 0.2),
                inset 0 2px 15px rgba(0, 0, 0, 0.2);
}

label .indicator {
    position: absolute;
    top: 0;
    left: 0;
    width: 40px;
    height: 40px;
    background: linear-gradient(to bottom, #444, #222);
    border-radius: 50%;
    box-shadow:  0 2px 5px rgba(0, 0, 0, 0.5),
                inset 0 1px 1px rgba(255, 255, 255, 0.1);
    transition: .5s;
/* ---------- faz o botão se ficar menor ---------- */
    transform: scale(0.9);
/* ----------------------------------------------------- */
}

label input:checked ~ .indicator {
/* ---------- efeito que faz o botão se mover ---------- */
    left: 40px;
/* ----------------------------------------------------- */
}

/* ---------- bolinha dentro do botão ---------- */
label .indicator::before {
    content: '';
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 5px;
    height: 5px;
    background: #f00;
    border-radius: 50%;
    box-shadow: 0 0 2px #f00,
                0 0 5px #f00,
                0 0 10px #f00,
                0 0 15px #f00,
                0 0 20px #f00,
                0 0 25px #f00,
                0 0 30px #f00,
                0 0 40px #f00;
}

label input:checked ~ .indicator::before {
    background: #0f0;
    border-radius: 50%;
    box-shadow: 0 0 2px #0f0,
                0 0 5px #0f0,
                0 0 10px #0f0,
                0 0 15px #0f0,
                0 0 20px #0f0,
                0 0 25px #0f0,
                0 0 30px #0f0,
                0 0 40px #0f0;
}