In the aftermath of global annihilation, Mushroom 11 gives rise to a bioluminescent blob that looks like someone made radioactive jello in a murky swimming pool. It expands, contracts, squeezes and climbs through dilapidated nooks and crannies, never losing its total mass while the player prods it into motion. It's easy to play and hard to look away.
The quirky growth must use its weight and mass in clever ways to advance, be it creeping through the windows of a skyscraper about to crumble, splitting itself to trigger simultaneous mechanisms, or to roll past the attacking arms of a mutated plant. The trick is to realize that your touch (or mouse-click) removes adjacent pieces of the blob, which then immediately regrow, attached elsewhere. Closer observation shows it to be a living lattice of gelatinous material, moving and shifting its weight as it grows in response to your prodding. This makes Mushroom 11 a slower, methodical game, and different from fluid manipulation games like Pixeljunk Shooter.
The other trick to Mushroom 11, according to designer Itay Keren, is to teach players how to handle their blobs without resorting to text and obvious tutorials. The game is striving for subtlety, both in its story of how the earth came to ruin, and in its teaching phase.