Acid Drop is a puzzle game for the Atari 2600 designed by Dennis Kiss. The game was published by Salu Ltd in 1992 and was the last 2600 game released while the system was still be manufactured.
The game is similar to Sega's Columns which had already been released in arcades. In Acid Drop columns of three differently colored pieces fall down into the play area and the player must move the falling pieces around and change the order of the colors to line them up with other columns that have already been dropped. When a horizontal or vertical line of 3 or more drops of the same color is made those drops are removed from the board.
The goal is to keep the game going as long as possible by continually removing drops from the board, when the drops reached the top of the play area the game ends.