If you like puzzles...
There are sveral different methods of flipping them over including parallel lines and using the border. In the tetris-esque main mode you have to flip tiles as quickly as possible. This is where the fun lies and there is a satisfying sound to getting complete lines that just begs you to come back for another go.
In the puzzle mode you have as much time as you like (provided your ds can handle it) to come up with a solution to a particular.
Poplarium stimbles when it comes to presentation and it is just soooooooooo lacklustre.
Where it suceeeds however, is in providing pick up and play gameplay and you will find yourself always coming back for a 10 minute game.