Unlock clasic Tetris on the Teris Worlds GBA cart. On the Main Menu screen move the highlight to the Marathon option. Hold down the Left Shoulder Button and press Select. On the Marathon game selection screen there will be a new game option called Popular. This is the classic version of Tetris that everyone knows and loves.
Holding the R button will make the vortex on the main menu spin clockwise and holding the L button will spin it counter clockwise.