Today, the Biauron, as you might guess from its name, it's related to the auron or golden section, it's one of my favorites of the orthogons.
We begin as usual, with a square.
Then use the compass (set to over half of the line) to find the half way point of the square.
On the lower half of the square draw a diagonal from top left of the half to bottom right.
Set your compass with the point on the left half of the square and arc up to meet the diagonal line.
From the bottom corner on the right set the compass from the diagonal line arc to the left line of the square.
Set your compass on the point where the arc and the square meet, point on the point and set the lead to the bottom of the square and make a semicircle.
Draw the top of the biauron where the semicircle ends.