Zoo Keeper isn't all that complex of a game. The goal is to arrange animals of the same species into a line of three or more. Once accomplished, these animals are captured, disappearing from the screen, with a new stack of animals falling from the sky. The more animals captured, the more variation amongst the species on the playing field and the faster the timer ticks down.
Lining up the animals is simple enough. Finding two adjacent animals, the player touches both of them with the stylus to temporarily swap their positions. If no line is formed by the swap, each animal reverts to their original position. Alternatively, players can use the D-Pad and A button to command the animals, though this is a tad more cumbersome than stylus control.
Aiding the player in their capturing escapades are special panels that, when activated, remove all instances of a species from the playing board. Also useful are the binoculars, which highlight all possible lines available to the player.
While gameplay occurs on the bottom screen, the top screen is used to display an animated image of the current "Lucky" animal, that is, the species worth double points for the round. After capturing a certain quota of animals, the specifics of which are also displayed on the top screen, a new round begins, complete with higher quotas and a new "Lucky" animal.
An objective-based Quest mode helps to shake things up, requiring players to master the intricacies of the game to pass its ten stages. Also available are Time Attack, Tokoton, a sort of endurance mode where quotas begin at 100, Two Player Battle and the standard Zoo Keeper mode. Problem is, apart from Battle, they all make use of the same gameplay mechanics and items.
The goal of Two Player Battle is to whittle down your opponent's timer. New power-ups, such as the timer-restoring heart of the color-changing bucket, help to keep things from getting too boring. One-cart multiplay means that opponents only need a Nintendo DS of their own in order to partake.
Computer-controlled opponents in Battle mode would be nice, as some may not know other DS owners. As it stands, it's a little upsetting to see the only mode that tosses messes with the actual gameplay limited to two players.
Another issue would be the beep-boop nature of the game's soundtrack. Simply put, the tunes are annoying, and not in the highly-infectious-ditties-that-get-stuck-in-your-head-for-days way. Rather, the tunes are more obnoxious in a race-to-turn-the-volume-down sense. While nothing that ruins the game, it's still an annoyance.
Finally, it's hard to justify plopping down $40 for Zoo Keeper when a Flash version can be found for free on the Internet. Sure, it's not the same thing as playing it on your DS, but that's a lot of money to pay for a portable version of Zoo Keeper. A lower price point would make this easier to recommend.
Regardless, Zoo Keeper is a quality puzzler for the DS. Furthermore, it's one of the few games out that makes legitimate use of the touch screen. At $20, Zoo Keeper would be a must-have for any puzzle-seeking DS owner. But with its $40 price tag, only the hardcore need apply.