How to Create dark theme using Slider in CSS ?

/* Default light theme */
:root {
    --primary-color: #302AE6;
    --secondary-color: #536390;
    --text-color: #424242;
    --background-color: #fff;
    --heading-color: #292922;
}

/* Dark theme */
[theme="dark"] {
    --primary-color: #9A97F3;
    --secondary-color: #818cab;
    --text-color: #e1e1ff;
    --background-color: #161625;
    --heading-color: #818cab;
}

/* Adding css variable in our webpage */
body {
    background-color: var(--background-color);
    color: var(--text-color);
}

h1 {
    color: var(--secondary-color);
}

a {
    color: var(--primary-color);
}

/* Slider styling */
.theme-switch-container {
    display: flex;
    align-items: center;
}

.theme-slider {
    display: inline-block;
    height: 34px;
    position: relative;
    width: 60px;
}

.theme-slider input {
    display: none;
}

.slider {
    background-color: #ccc;
    bottom: 0;
    cursor: pointer;
    left: 0;
    position: absolute;
    right: 0;
    top: 0;
    transition: .4s;
}

.slider:before {
    background-color: #fff;
    bottom: 4px;
    content: "";
    height: 26px;
    left: 4px;
    position: absolute;
    transition: .4s;
    width: 26px;
}

input:checked+.slider {
    background-color: #66bb6a;
}

input:checked+.slider:before {
    transform: translateX(26px);
}

.slider.round {
    border-radius: 34px;
}

.slider.round:before {
    border-radius: 50%;
}