Hey, excellent visuals and ‘polish’ to the gameloop with start and endscreens as well. As you mentioned, you would benefit here from balancing the challenge. It’s too easy! :p Some sound would be fun too. I love your use of dithermark to create variants.
One simple thing would be to add an attribute like flipped to each squirrel. If moving left then flipped should be true and you display the sprite facing to the left. Otherwise, display right-facing sprite.
You could load two versions of the image. Some game engines have a way to flip sprites. I don’t think p5 does natively but one option:
if (facingLeft){
//need to add push and pop if woven into a larger program since scale will affect other draw functions afterwards
scale(-1, 1)
image(img,-width/2,height/2);
} else {
image(img,width/2,height/2);
}