Euclid Elements Book 1 Prop 43 (Incorrect)
Proposition: https://mathcs.clarku.edu/~djoyce/java/elements/bookI/propI43.html
Try moving the point A around (top left corner)
This corresponds to an incorrect but interesting attempt to make a geogebra for this proposition
If the point A is to the right of point B, then you will see two parallelograms, one blue and one green. The theorem says that the two parallelograms are congruent