Great game ! Found two bugs, one is the appareance of purple one (fearing the ghost) which looks like a white square (only happens sometimes) ; the second one is at the end, by reaching the highest level I cannot go back, nor play, nor save.
Thanks a lot for finding the bugs. I am going to fix them for a later version. I think I have never made it to the highest level in my playthrough. Probably only did 5 upgrades.