Left/right arrow keys or A/D keys to change the value of c. Hold space key to change it 100 times faster. Hold X key to change it 100 times slower. Press 1 through 6 numeric keys to see examples.
On the ith loop, the pen sprite moves (zoom) steps and turns (a + b * floor(c * i)) degrees clockwise. I tried different parameter values in my project https://scratch.mit.edu/projects/787738313/ ( which is a solution to Code Golf Grid Challenge 2 by @Scratch-Minion https://scratch.mit.edu/projects/735831347/ ) and got lots of interesting patterns.