Hatris is a puzzle video game developed by Alexey Pajitnov for Bullet-Proof Software. It was also released as a standalone arcade console. Hatris' gameplay is similar to Tetris (also designed by Pajitnov), in that game objects falling from the top of the screen must be arranged in specific patterns to gain points and to keep the play area clear. In Hatris, hats of different styles fall from the top of the screen and accumulate at the bottom. To eliminate hats from the play area, five hats of identical style must be stacked. Different style hats stack differently.