This game is beautiful and well made, but it is absolutely wickedly hard. Human visual working memory is fairly well studied and its limits are around 3-4 items when you lay things out in a grid like this. Your 3x3 grid is definitely doable with chunking strategies for most people, but most people would not be able to complete the 4x4 grid. I can see this as being a fairly fun way to actually practice visual working memory if you added the ability for people to go into a "test mode" perhaps where they could select how large the grid was and how many unique elements, etc. Although feel free to ignore that, I'm doing my phd in cognitive science right now so I'm pretty biased when thinking about games that feel like experiments haha.
Overall a really unique and uniquely challenging submission :)