BlockForge X for Mac

From Xenquin Software:

BlockForge is a version of the classic game "Tetris", in which you are in control of blocks falling in a pit. Your objective is to form solid horizontal lines, which will clear and give more room for new blocks. The game ends when the blocks reach the top of the pit. Unique to this game is the ability to entirely customizable playfield graphics and sounds. The player may add additional "Themes" into Themes folder, giving the game different graphics and sound effects. There are two themes bundled with BlockForge, the "Iron" and "Skyscrapers". Custom themes may be downloaded from the Internet, or made by players themselves with resource editing tools. In addition to normal tetris gameplay, BlockForge also has two additional single-player modes called "Time attack" and "Turbo", and even a two-player multiplayer mode which allows two players to play against each other on one computer.