The world is destroyed, if you happen to be human.  All that's left is a shattered wasteland of twisted metal, rusted signs, deteriorating walls covered in now-meaningless graffiti, and the remnants of whatever managed to survive mankind's final fate.  One of those remnants is a green fungus that's got no problem at all with the broken world because, while the wasteland is an utter disaster from humanity's point of view, if you're an ambulatory blob of DNA-absorbing plant life then the world is merely tricky rather than destroyed.

Mushroom 11 features a weird fungal organism traveling through a side-scrolling world by erasing its unnecessary bits and growing new cells in the direction it wants to go.  I got a look at it during PAX East and came away impressed, with the game easily stealing about 20 minutes of valuable show-floor time, and now that I've got a second chance to play it in the peace and quiet of home it's even better.  The latest build is almost identical to what I got to play last spring, barring a few tweaks to the level flow to prevent the earliest parts of the game from kicking the player's teeth in, but it's always nice to be able to hear the creepily atmospheric music and take the time to experiment a bit.  The creeping fungus of Mushroom 11 doesn't control like anything else out there, so it's a lot of fun to play with different techniques to make it grow properly.

Because it's a plant, the mushroom can't move.  Left to its own devices it would just sit there quietly thinking its mushroomy thoughts, completely indifferent to the rusting desolation around it.  Your job, then, is to shepherd it around the levels, destroying the parts of the organism that aren't where they ought to be so that new parts will grow elsewhere on the mass.  You've got no control over where new cells pop out, so building a specific shape for the areas that require it involves careful editing, but it will go where you want eventually so long as you don't accidentally erase a part you need.  Most of the time you'll be carefully trimming the growth into shape, encouraging it to grow onto ledges and anchor points in the wall, but because it grows disturbingly quickly you can send it along at a good pace when necessary.  It needs to be on the ground to regrow, however, so any momentum for sailing over a gap has to be there before the jump rather than generated during.  Trim away too much mass mid-air and all that's left is a single small cell that will easily fall into a hole and burn up in the purple toxic sludge.

Getting through the two-level demo is tricky, but chasing after all the DNA gets downright mean.  Sonic has rings and Mario gets coins, but mushrooms, apparently, like DNA absorbed from the bodies of the plants and animals found along the way.  The insects, spiders and Dragon Quest-style slimes all live in out of the way areas that require very careful maneuvering to ingest, and you'll need to exercise every trick learned along the way while devising a few new ones to collect everything.  There's a lot of careful thought put into the puzzle design of even these two first levels, and the mushroom needs to stretch, balance, teeter precariously near certain doom, and almost defy gravity to find every nook and cranny, not to mention defeating the level bosses.  The ruined world may be little more than a playground for the terrible growths feeding off the ashes of civilization, but there's no reason what survives can't enjoy a rewarding, atmospheric challenge traversing the bones of humanity.