This has to be the next Tetris, Highly addictive, and very entertaining.
In Lumines, you line blocks up by colors, usually 2 colors in the level. To score points, you line up the colors in a box formation, if you can make a box out of the current box; it gives you more points, and so on. While you play, the background shifts and music plays. When you place blocks, it plays a certain note that fits with the music also, very cool.
This game is very addictive. You will find yourself very anxious to get to the next level to find out what the next song and color theme is going to be.
The vs. mode in Lumines is pretty cool, but the main game mode is what I played most of the time when I had my PSP.
If you have a PSP, you have to have Lumines.