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Stack 'em is a turn-based puzzle game in which you must make groups of the same animal types to send them on a vacation.

Grab any animal you choose by clicking on it, no matter of how many other animals are stacked on top of it. Move that animal (or group of animals) to any other part of the playfield and drop it by releasing the mouse button. By placing five or more animals of the same type next to each other (touching either vertically or horizontally), you'll make a match and those animals will disappear. Any animals stacked above the matching animals will fall into the empty space left behind.

Every time you make a move, the pressure gauge on the left side of the screen gets closer to the red zone. Once the needle gets into the red zone, you have only one move before a new row of animals comes into the playfield. If any animals fall over the fence as a result of a row being added, you'll lose one life pack per animal from the right side of the screen.