Sillage

Sillage, French for the wake a boat leaves behind, is a small browser game with no goal. You play a blob that swims toward your mouse or finger, and fast currents carry you into the next world. Its creatures and backgrounds draw on Ernst Haeckel's Kunstformen der Natur.

The creator introduced the project with a Hacker News post. They say they had wanted to make something like it for years, since reading Jenova Chen's thesis on flow in games.