The project below starts with one pinwheel-drawing script: a repeat 21 loop that moves forward 100, back 70, and turns 360/21 degrees, plus small scripts to put the pen down and clear the stage. Make five copies of the script (right-click its topmost block and choose "duplicate") and modify the copies so they draw pinwheels with 3, 4, 5, 6, and 12 branches.

Then compare two of your scripts: they're essentially the same, only some input values change. Turn them into a single general pinwheel block with an input for the number of branches, so one block can draw all of those designs.

Your work autosaves (and you can use the Save button); earlier versions are available from the Revisions dropdown.