Zoo Keeper is nothing but Bejeweled with animals. Basically, you swap 'em horizontally or vertically, one next to each other. If you get three or more of the same species in a row, they dissapear, and the animals above fall down. You can, of course, plan ahead and make chains, which is really fun. That's basically it. But man, does it get addictive!
The game features a whole variety of game modes. You can try Mission Mode, Time Attack, Standard, and others that I can't remember right now ^_^ But the game has great replay value. Multiplayer is there too, single card! There are items in multiplayer and the matches can become quite exciting.
The graphics are good for a puzzle game, but they could've been more varied. The sound is good but could've also been more 'exciting' or frantic, if you will.
Zoo Keeper is a game that you won't be able to put down for a while. Once you do, you'll move on to something else, and one fine day you'll remember about Zoo Keeper and you'll play it again for hours and hours, just like before. Great puzzle game.