I've actually never played any of the mainline Rayman games before this one, but apparently you don't need to as this is about as simple as it can possibly get. It's an "endless runner" where you only use one button, the function of which varies depending on what set of levels you're in.
The game is broken up into five initial collections of eight or nine levels each. While you're always able to jump in each collection, some give you added abilities like floating with your propellor ears or punching through walls. The goal of each level is to collect as many fireflies as possible, you need most or all of them on each level to get the highest ranking, which in turn is needed to unlock the final collection of levels.
The levels are very small and mobile-focused, averaging out to maybe a minute each in length. So the game really emphasizes collecting all the fireflies and the score/time attack aspect. This part can get a bit tedious if you don't like repeating the same levels over and over and over trying to make a series of really finicky jumps.
Controls are usually the bane of mobile platforming, and simplifying the game down to "endless run" style really worked here. For the most part the game feels very satisfying, but if you're playing on Windows 8 and using a mouse, be warned they didn't bother to add right mouse button functionality. This is only a problem in the "Punch" levels, where you have to manually press the punch button by clicking on it. The right mouse button isn't used for anything else, so this is kind of a crappy oversight. If you're gonna put stuff in the Microsoft Store, make sure it works fully on all the devices that access that store, guys.
The game looks nice, and if you're on a touchscreen device you can't really fault the gameplay, other than the inanity of characters refusing to ever stop or turn around that's inherent to the "endless run" genre. The music ... more of a mixed bag. It was decent outside of this one Chipmunks-like song that is incredibly annoying. I hate the Chipmunks though, I never understood how they were popular, so YMMV.