Zoo Keeper is an online puzzle game developed by Robot Communications that was later ported to the Nintendo DS by Japanese video game publisher Success. The game was then brought to American and European shores by Ignition Entertainment.
In Japan, before the release for Nintendo DS, Success released this game for Game Boy Advance and PlayStation 2 with alternative name Zooo. The PlayStation 2 version of this game was later released in Europe by 505 Game Street under the title Zoo Puzzle.
Symbols are aligned by swapping one tile with one next to it. If this makes a line of three or more matching tiles with either of the swapped tiles, the tiles stay in this position and the line disappears. If no line of three or more matching tiles is formed, then the tiles swap back to their original position. Lines can be horizontal or vertical, and combinations can mean that many lines disappear at the same time.
When tiles disappear, any tiles above them on the screen fall down to fill the space. If this results in a further line of three, this line also disappears. This is called a 'chain'.
On the DS version the upper screen shows a favourite animal, for which captures generate increased points (and an amusing animation). It also benefits from the touch screen operation, and the opportunity to battle another DS owner. Other versions allow two players to play at once on the one screen.
The game is similar in concept to Bejeweled, a game developed for PCs and later ported to other platforms. However, there are some crucial differences. The aim of Bejeweled is to not run out of moves, whereas if this happens in Zoo Keeper the screen is cleared and you earn bonus points. Furthermore, Zoo Keeper has a number of additional modes, such as Quest and Time Attack, which expand the game considerably.
One very important aspect that sets Zoo Keeper apart from Bejeweled and its many clones is the ability to switch tiles while another move is still 'in progress'. This allows the player to set up chains, or to 'fake' chains by creating multiple rows of three in quick succession.
If no moves are available the screen is reset, but the clock keeps ticking. Similarly whilst chains are formed after you clear a level the clock keeps ticking though you are locked out from playing, which can be frustrating in the 6 minute 'Time Attack' mode.
One well known challenge when playing Zoo Keeper is the inability to find a valid move, which often seems to become more common after a long period of gaming. To combat this, players are able to use the "binoculars" tool to show them the position of any unexploited moves, but this tool has limited use. This inability to see the next move is known as 'Zoo Keeper's Block' and this term has been used for other puzzle games as well.
Different tactics are useful in different modes. For example, in the classic mode it can be helpful to leave one set of animals untouched in order to amass the highest possible score in each level (as level progression increases the speed at which the timer bar erodes). In Time Attack it is helpful to move levels as fast as possible as each level change increases the points per capture.
The zookeeper responds to your efforts with critical comments, and often applies a multiplier to your score so far, rather than a set number of points for each level. A good performance may double or even triple your total points, but a poor performance can reduce your total by 70% and declare you a loser.
This mode has attracted much criticism, as the randomness of the challenges and reward system mean that progressing is as much a matter of luck as it is of skill. In particular, in reference to the seventh challenge listed above, Stuart Campbell wrote in his extensive review that the game doesn't take into account that the random new items filling the places of the captured animals can inadvertently generate new captures, making your challenge impossible. On the other hand if you can avoid being eaten away by frustration, this randomness does create greater granularity in scores, and add to the game's endurance, as you constantly hope for a lucky run to beat your top score!