A very interesting puzzle game! I like the idea and how it was developed. However I found a bug where if I'm in a position where I can put the piece, it disappears, which made me think it was not possible to place it there. This left me confused for a little while until I clicked in that position randomly. I also think a simple explanation of the rules would be great, because at first I thought I had to place the negative pieces on the negative regions, while it is actually the opposite. Good job!