Chain Reaction is a one or two-player shareware "falling block" and tile-matching puzzle game. Blocks comprising bricks of different types descend from the top of the screen. When the player lines up the blocks so that three or more bricks of the same colour are in a row, (vertically, horizontally or diagonally), they explode scoring bonus points and making space for more blocks to be positioned. As they fall the blocks can be rotated and steered, in addition the order of the bricks within the blocks can be changed. Blocks fall faster as the player(s) progress through the levels. Other features of this game include difficulty settings, choice of start level, and choice of block set. The shareware version made four single player levels available. The full, registered, version offered a two player mode and "infinite levels of gameplay".