Shift key & flag for turbo fast frost fern growth. Adjust a, b, c, and transparency, as you wish. R to reset to default values of a, b, and c. Fractal, self-similar across scales. I like better my DLA versions of window frost which aren't really fractal. Spacebar changes background.
Compare to my DLA window frost fern (better I think): https://scratch.mit.edu/projects/635586780/ This one here is modified from my "Growing Fern Garden (Barnsley Ferns)" with ferns completely reshaped, distorted, and repeated to look like window frost ferns, the kind seen on windows when freezing and humid. Compare this frost fern to my diffusion limited aggregation version: https://scratch.mit.edu/projects/939646959/