Tetrix
Description
Tetrix is a Tetris variant for one or two players. There are no significant deviations from the original Tetris rules, but as the player advances to the next level, the tetromino pieces not only fall down faster, but the blocks they are made of also change their shape: from the usual square blocks in the first level to balls, diamonds etc. However this is only a cosmetic change that does not affect gameplay in any way.
Additionally, there is a bonus game called Tank vs UFO that can be played from the main menu.
Tetrix was originally marketed as shareware but the author eventually released the full registered version for free. The shareware version only includes the one-player mode and no bonus game, and during play the preview of the next tetromino piece is occasionally concealed with a nag screen urging the player to register.