I play tetris too (hkgwife)

A detective doesn't have supernatural powers. There's no way to predict the answer from the beginning. Instead, the ideal detective begins by imagining as many possible scenarios as they can. They envision these possibilities without prejudice, without bias, using only their logic and common sense. Then, as they investigate, they test what they find against each of these possibilities. Of course, me telling you this doesn't mean you'll be any good at detective work. But beyond using that to solve this particular mystery, you should keep it in mind for the future.