More of a Musical Tool than a Game
In Electroplankton you choose one of several little sea creatures to interact with. Each creature behaves in a different way and subsequently produces different sounds. The initial fun in the game is actually exploring the different sounds that can be made through different actions on the stylus and with the DS game pad. For example one creature, Tracy, acts through the drawing of line on the DS screen. Different curvature and speed with which you draw the lines will cause the Tracy organisms to produce different sounds as they follow the path you draw. It can be a challenge not to simply create a cacophony.
As an amateur musician and fan of new means of sound expression, I think this game is a neat tool - particularly for the $35 range. You just don't find interesting sounds for that cheap.
As a game, I have to say this one fails. I imagine one would be somewhat hard-pressed to find the quirky creatures of this game entertaining for an extended period of time.
It wasn't until I hooked my DS up, through the head-phone port, to my computer that I really started to see this "game" in a new light. I simply laid out tracks using a recording software (Acid Pro or Audacity for free). I then proceeded to actually record the sounds that I made - a feature that was unfortunately missing in the game itself (perhaps for some greater artistic reason that doesn't make sense to me). I then was able to loop those tracks and add sounds of my own.
In general, I would not recommend this game to gamers. It doesn't have any ultimate goal, there is no accruing of points or anything to really brag about (as you can't readily save your results). Rather, this game should be purchased by those who either simply enjoy artistic multimedia expression, or intend to use this game as an instrument of sorts.