The design is good. The author, in each of his levels, offers a different theme, sometimes also with different gimmicks and ideas. It was really fun to go through the levels, even if it's not a game to complete, since you can access everything from the beginning. Not much more to say, I guess.
The aesthetics, too, are good. Vanilla elements, enriched with custom palettes that looked really good in some levels, less good in others. I liked the fire rain in "The sky is on fire!", even if the effect looks a bit laggy.
Overall, a fun hack. One of those to play if you feel lazy and want to play a good hack without it being too complicated.