Electroplankton
Electroplankton is an interactive music video game developed by the Japanese interactive media artist Toshio Iwai and published by Nintendo for the Nintendo DS. The game involves the player interacting with different kinds of plankton to make various musical melodies.
In Super Smash Bros. Brawl
There is a hidden Electroplankton-themed stage within Super Smash Bros. Brawl. The layout is based on the Hanenbow tract, consisting of a stem poking out of water with six leaves(three on each side) serving as the platforms. The leaves darken from green to red as they take damage. Small plankton jump out of the water and bounce off the leaves, leaving a resonating sound that is deeper in pitch depending on the color of the leaf. This stage is particularly strange because it is the only one where you cannot swim in its water, and it is also the only one to have completely interactive music. It is unlocked by clearing Event 28: Flower Blooms in the Echoes.