I'm not sure what the exact version you have is, but that type of handheld has been around for over a decade easily. I'm sure it's the same basic chip shared in all models, something off the shelf that any company can buy and make into their own product.

Basically that type of handheld would have several built in games. One being a Tetris clone, but there should also be a snake/serpent clone, and some other similar types of simple games. I used to see these regularly in various dollar stores over the years. Unless somehow what you have is different, maybe only featuring one game instead of several.