Check out example codes for "box shadow". It will help you in understanding the concepts better.

Code Example 1

/* offset-x | offset-y | blur-radius | spread-radius | color */
box-shadow: 2px 2px 2px 1px rgba(0, 0, 0, 0.2);

Code Example 2

/* Keyword values */
box-shadow: none;

/* offset-x | offset-y | color */
box-shadow: 60px -16px teal;

/* offset-x | offset-y | blur-radius | color */
box-shadow: 10px 5px 5px black;

/* offset-x | offset-y | blur-radius | spread-radius | color */
box-shadow: 2px 2px 2px 1px rgba(0, 0, 0, 0.2);

/* inset | offset-x | offset-y | color */
box-shadow: inset 5em 1em gold;

/* Any number of shadows, separated by commas */
box-shadow: 3px 3px red, -1em 0 0.4em olive;

/* Global keywords */
box-shadow: inherit;
box-shadow: initial;
box-shadow: unset;

Code Example 3

box-shadow: 0 0 10px 0 rgba(0,0,0,.1);
// copy this

Code Example 4

#example1 {
  box-shadow: 10px 10px 8px #888888;
}

Code Example 5

#example1 {
  box-shadow: 5px 10px;
}

#example2 {
  box-shadow: 
    5px 10px #888888;

    }

Code Example 6

#example1 {
  box-shadow: 5px 10px;
}

#example2 {
  box-shadow: 
    5px 10px #888888;

    }

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