The Pen Lab
Three experiments with the same pen. In each one you decide first, then the pen runs.
The turn dial
Pick a number of sides and a turn. Will the pen come back to where it started, facing the same way?
Two programs, one picture?
Different programs can draw the same picture. Decide before you see them.
Fix the pen
Each program draws the wrong picture. Find the one line that is wrong, then pick the change that fixes it.