shape-margin

shape-margin: 0;

shape-margin: 20px;

shape-margin: 1em;

shape-margin: 5%;

<section class="default-example" id="default-example">
  <div class="example-container">
    <div class="transition-all" id="example-element"></div>
    We had agreed, my companion and I, that I should call for him at his house,
    after dinner, not later than eleven o’clock. This athletic young Frenchman
    belongs to a small set of Parisian sportsmen, who have taken up “ballooning”
    as a pastime. After having exhausted all the sensations that are to be found
    in ordinary sports, even those of “automobiling” at a breakneck speed, the
    members of the “Aéro Club” now seek in the air, where they indulge in all
    kinds of daring feats, the nerve-racking excitement that they have ceased to
    find on earth.
  </div>
</section>

.example-container {
  text-align: left;
  padding: 20px;
}
#example-element {
  float: left;
  margin: 20px;
  width: 180px;
  height: 180px;
  border-radius: 50%;
  background-color: rebeccapurple;
  shape-outside: circle(50%);
}

/* <length> 値 */
shape-margin: 10px;
shape-margin: 20mm;
/* <percentage> 値 */
shape-margin: 60%;
/* グローバル値 */
shape-margin: inherit;
shape-margin: initial;
shape-margin: revert;
shape-margin: unset;

<section>
  <div class="shape"></div>
  We are not quite sure of any one thing in biology; our knowledge of geology is
  relatively very slight, and the economic laws of society are uncertain to
  every one except some individual who attempts to set them forth; but before
  the world was fashioned the square on the hypotenuse was equal to the sum of
  the squares on the other two sides of a right triangle, and it will be so
  after this world is dead; and the inhabitant of Mars, if one exists, probably
  knows its truth as we know it.
</section>

section {
  max-width: 400px;
}
.shape {
  float: left;
  width: 150px;
  height: 150px;
  background-color: maroon;
  clip-path: polygon(0 0, 150px 150px, 0 150px);
  shape-outside: polygon(0 0, 150px 150px, 0 150px);
  shape-margin: 20px;
}