Mushroom 11 is a side-scrolling puzzle game in which you must guide an amorphous organism across obstacles. The player controls the fungus-like blob by clicking and holding and then pointing in certain directions to guide the liquid-like substance in a certain direction. Rather than moving the organism, the player actually removes parts of the organism that then regrow as new cells at the other end of the organism in the specified direction.
There are many obstacles to overcome with challenges that involve physics. The organism needs to be guided into tight spaces, it can balance and climb, move or launch objects, it needs to be split up and so on. The same mechanic is kept throughout the game, so if the organism is split up and the player deletes one part, it regrows on the other right away. The same technique can be used to get past solid walls.
Next to completing the levels grouped in seven chapters with a boss in each one, it is possible to absorb small plants in hard to reach locations as an optional objective. The game was started as a prototype at the 2012 Global Game Jam.