Changing up Tetris once again, this time instead of matching colors or rows, you're supposed to create a cycle (chain of arrows, forming a loop) although it can be as small as two arrows facing each other. You'll definitely need to form bigger cycles to beat the computer on even the entry mode, though. Controls for single player are arrows, Z and X, the two-player mode adds T/F/H/V for the other player, but switches up the action keys to / and _ for the player using the arrows, while the other player gets the original Z and X.
There's several game modes, including Conquest, which apparently leads to a series of CGs with adult content. However, I'm terrible at this game, and the authors were savvy enough to CRC check all the images, to prevent the old "switch images with the title" technique for seeing all the CG.