This puzzler will keep you guessing because thinking about it too much holds back what made it so special in the first place. As a mash-up of now-familiar and decades-old series, just putting these two games together is almost enough. The game's at its best and shines when you play against other human players. There's a healthy variety of modes that introduce new parameters and objectives (Versus, Party, Swap, Fusion, Big Bang), but the core game itself remains largely the same, as it should. And thankfully, when playing the single-player story mode, the game grants concessions to people who are still grappling with the learning curve of either Puyo Puyo or Tetris -- if you're stuck on any single level after a couple of tries, it lets you skip ahead and continue on. That doesn't help you learn how to play the game any more, but it at least lets you keep trying in a number of ways as you hone your core skills.
In practicing against the computer in the different modes, it's odd that if you lose, it makes you sit and watch the rest of the game play itself out as the AI tries to outdo itself and win. You can be sitting for multiple minutes, watching the computer play itself and have no way of skipping past it. It's also difficult to figure out when you're sitting there watching to see why the computer is doing what it's doing to pick up on new strategies; the in-game tutorials are also too basic to help you learn tactics and focuses solely on the controls. As such, introducing play to newcomers is rather lacking. It assumes you already love both series (which makes sense), but in practice, it winds up keeping you from being able to pick up as much as possible as quickly as possible. On the other hand, Tetris is Tetris and Puyo Puyo is Puyo Puyo. It definitely delivers on combining these two but could have done so a little more smoothly.