It's a mutation simulation with colorful shapes. You will get a autogenerated sequence of 8 shapes (on my screen at least, you might get fewer for a smaller screen) then you can choose to start mutating from either shape. The new mutated shapes have the same option to mutate from so you can mutate until you're happy with the said shape. Once satisfied you can add it you your garden (your repository of shapes you chose to keep). You can fork from any of the shapes and mutate them further. There's a refresh button that autogenerates new shapes, took me a while to spot it.

I personally find this very interesting both conceptually and visually. I've been doing myself a lot of autogenerated graphics in Racket from lists of features but never went as far as to show it to HN.