Check out example codes for "scss transition mixin". It will help you in understanding the concepts better.

Code Example 1

/* Mixin for transition css */
@mixin transition($for: all, $time-in: 250ms, $type: ease-in-out, $time-out: 0s) {
    transition: $for $time-in $type $time-out;
    -moz-transition: $for $time-in $type $time-out;
    -webkit-transition: $for $time-in $type $time-out;
    -o-transition: $for $time-in $type $time-out;
}

/* IE10 (the first stable version of IE to support transition)
does not require the -ms- prefix. */

Code Example 2

transition

Code Example 3

div {
  transition: all 0.5s ease;
  background: red;
  padding: 10px;
}
div:hover {
  background: green;
  padding: 20px;
}

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