Check out example codes for "css glow effect". It will help you in understanding the concepts better.

Code Example 1

div {
    width: 150px;
    height: 150px;
    background-color: #fff;

    box-shadow: 120px 80px 40px 20px #0ff;
    /* in order: x offset, y offset, blur size, spread size, color */
    /* blur size and spread size are optional (they default to 0) */
}

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