You're one of the few survivors of a post-apocalyptic future in which all humans were wiped out. Oh, you're not a human; you're some sort of spore-mold thing. In order to continue to evolve and survive, you have to trek across the ruins of the humans' world, avoiding poison, fire and other mutated denizens of this dark world, while collecting their DNA to enhance yourself as you go.
The environments are composed of near elements that form the areas you'll be solving puzzles and "platforming" in and background elements, which depict the post-apocalyptic world that you're inhabiting. These background elements provide additional interest and often have comical elements, so take the time to check them out as you play. The music has an industrial ambient feel and does a good job of helping to set the mood. Actually, I was impressed by the level of polish in Mushroom 11. The music and graphics are nicely handled and do a good job of setting the scene, presenting the puzzle and, otherwise, staying out of your way.
Ever squeezed a ketchup packet back and forth between your fingers? Chances are, if you've done it once, you've done it way more than just once. It's kind of like popping those air bubbles in bubble wrap. There's something entertaining and satisfying about the way that constrained liquid behaves: when you squeeze it here, it inflates another part over there. The same concept was made into a toy called a "water wiggle" - which is cylindrical tube filled with liquid. You squeeze it, the liquid squishes to another part, and the toy moves in the direction that the water just squished. Sometimes they can seem to have a life of their own.
Mushroom 11 took this concept and built a videogame around it. Instead of "squeezing," you're killing off part of your organism, but the behavior is much the same. Removing part over here increases "pressure (to grow)" elsewhere. In order to move your organism around, you have to carefully prune here and there, shaping your colony into the shape needed for the puzzle at hand and herding the living part in the direction you need it to go. There are fluid dynamics, of sorts, at play here, as you'll see when your organism "wicks" up a thin tunnel.
All you can do is kill off part of your organism, using the mouse similarly to a eraser tool in a painting program. Press the Left Mouse Button and you'll erase a large circular area of your organism, use the Right Mouse Button and you erase a small area. However, with just these two similar actions, you will be forced to find more and more ways to interact with your environment. Do you make yourself round so that you roll better? Perhaps you have to find some way to "grab" onto something and knock it over. You may have to form your organism into a ramp to make something jump up into the air or leave a piece behind to keep a button depressed. All of this, however, comes from simply... erasing a bit here and there.
Mushroom 11 is a challenging puzzle game, but as unique as the puzzles are and as strange as the controls are, the most challenging aspect of the game is wrapping your head around exactly what you are doing and how best to move your organism and solve the puzzle at hand. Some of the puzzles can be solved by splitting your organism into pieces and leaving a piece behind in a strategic place, such as on a button that opens a door, allowing you to leave through the now open door. However, to move your main blob, you have to erase parts of it. Some of the regenerated mass will appear on the other part (the part you left behind), so you'll have to be careful to make sure you erase from both of the masses; you don't want to completely erase your main "moving" blob or your button pushing part, so be careful.
If you've ever erased anything in a paint program using an eraser tool, then you know what to do to play Mushroom 11. All you need is a mouse with two buttons. The left one erases a large swath, as I mentioned above, but it starts with a small circle and expands up to its normal size. You can use this to your advantage by only tapping your Left Button quickly when you want to trim small or medium size areas... or by holding it down and moving the mouse inward to carve away large areas without the slight delay as the circle grows to full size. (We're talking about a really short amount of time here, but it does offer some flexibility.) The Right Button starts and stays small, which can come in handy when you need to make minute adjustments or to hollow out your organism to force more mass to the outside. This can effectively make your organism seem "larger," allowing you to extend your reach a bit, when needed.
While the game's "gimmick" is enough to support a decent game, Mushroom 11 backs up the gimmick with solid presentation and a save game system that works well. That might sound like a strange thing to mention, but I've seen some horrors where gamesave systems don't work and ruin the experience and, more often, games won't offer save points frequently enough, leaving the player to replay a tough portion over and over. The save points in Mushroom 11 are frequent, basically located after each puzzle and they work. Every time I leave the game and return, I'm right back where I left off. Which is good, because Mushroom 11 is fun and a game I can see myself coming back to over and over. And, with the frequent save points, I can jump in, play through a puzzle, hit a new save point and leave; you don't have to set aside hours to play.
If you like puzzle games and you're looking for something novel, Mushroom 11 is definitely worth picking up. It's not like anything out there and can provide some interesting challenges.