Ways to improve on a classic do not include sticking it in an aquarium and adding a couple of fish. And then trying to sell people extra fish, even though you've already charged them GBP 6.80 for a game that's more than 20 years old. Welcome to the rubbishy underwater world of Tetris Splash.
Tetris Splash gets one point for being Tetris, one point for at least having an online mode and one point for being relatively cheap (assuming you don't bother with the DLC). But it loses points for ugly background graphics, the obligatory ghost block, the bad pacing, the expensive add-ons, the limited multiplayer options and having no sharks. If you're in need of a fix buy Tetris DS or play one of the free versions widely available on the Internet. Tetris Splash should be consigned to a watery grave.
