Like others before me have mentioned, Electroplankton is less of a game with clear objectives/guidelines or a beginning, middle, and end, and more of a "toy" that sort of functions like that of a musical instrument (not entirely accurate, I'll elucidate this later) or an early audio-visual experimentation on the DS. I say "toy" because there's two modes, and one mode dubbed "Audience Mode" actually has the game play itself more or less and automatically produce sounds, though you can still interrupt whenever you'd like to provoke sounds of your own alongside the CPU input, whereas "Performance Mode" is just strictly left to the player's discretion. Anyways, this is a collection of ten different minigames akin to tech demos on the DS that are generally controlled with the touch screen, though sometimes the D-pad can be used to produce waves that also create vibrations in the electroplankton. You generally tap the electroplankton or drag/draw lines to create some form of movement, and various tones are emitted based off the type of movement and specific minigame/feature interacted with. To its credit, the minigames are distinct enough: for example, the most famous minigame, "Hanenbow" (you may have heard of it from a little known game called Super Smash Bros Brawl) has you changing the angle of leaves on a plant and watching plankton bounce off of the leaves to produce notes that sound like a xylophone. Then there's a minigame called "Luminaria" where you can change the direction of arrows to alter the trajectory of the plankton on screen as they loop around and produce notes. And there's also a minigame where you can place plankton eggs and watch their smiley faces get bigger as they emit light and sound while slowly growing larger. There are also a few minigames that use the DS mic (as expected of most DS tech demo games), though these are mostly fancy recorders that will take your voice input and run it back to you with minor modification.

Perhaps I'm being a little harsh here, but I suppose I found Electroplankton a bit disappointing because there's a certain lack of depth to this all. That isn't to say that there needs to be depth in a plaything like this, but to try and elaborate where I'm coming from, I'm actually somewhat hesitant to use the "musical instrument" description, despite lack of a better term. Musical instruments have a sort of rhyme and reason to input and response: if you play a certain way or use a certain fingering/key, then you'd expect the same note(s) to come out every time. That generally doesn't really exist in Electroplankton for a couple reasons. Firstly, there really isn't a clear way to associate a certain tone/note with a certain response, or at least no tangible, marked up relationship that I can tell. And secondly, the actual interval of these notes taking place is usually within the span of a few seconds, so it's not like you're going to be playing Beethoven's 5th Symphony or even Hot Cross Buns with the tools you're given in Electroplankton. So as a result, it's really less of trying to create something memorable with Electroplankton, and more of a random and spontaneous jumble of notes and sound effects that are created when you mess with elements on a screen. It's still cool and all, but it feels like more of a one-off relic of its time than a genuinely memorable experience for me. Not that any of this really matters anyways, because the director of Electroplankton, Toshio Iwai, was very insistent on not including any built in save functions, and the developers wanted players to more or less "enjoy Electroplankton extemporarily and viscerally" and sort of get lost in the moment.

So maybe this is just overanalysis on my part and it's more of a case of "interesting, but you kinda had to be there." If you just want to peer upon a relatively unknown part of Nintendo's history or you feel like messing around with experimentations in game input and audio/visual responses, then give this a shot. Or put this on if your little siblings/cousins are begging to have some time on your DS and you don't want them mistreating your Nintendog or deleting your Pokemon Platinum save file with Arceus, I think this would work great for that case too. But otherwise, if you're just looking for a new instrument to learn/play and/or want to annoy your friends, maybe skip buying a physical copy of Electroplankton and just buy yourself an Otamatone; it's way cheaper and sometimes you just can't beat the classics after all.