The basic premise of the game is that you play as two different characters, but only one at a time. It starts out as a fairly simple side-scroller, but almost right away, you're taught how to solve puzzles by changing the "rules" of the universe.
The game itself is simple, and I mean that in a good way. A lot of modern indie games (that I've played) seem to cram a lot of excessive rules, mechanics, and ideas into a stream of levels and challenges that don't feel like they tie together. And what's more, a lot of the features that are built in get used once or twice in the game, then never get used again.
Four Sided Fantasy, on the other hand, uses two buttons and the control pad OR joystick (depending on how you want to play). You move, you jump, and you "lock" the screen, creating a hard edge that allows you to bypass walls simply by walking off one edge of the screen to end up on the opposite side.
All of that, combined with the gameplay itself, made this game super fun. Just FUN! It's a quick play (I spent a total of three hours making it through the levels, but didn't earn even half of the Trophies). That doesn't mean that it's unchallenging. I had to stop and rethink how I played the game, reimagining the rules of the universe to stop thinking linearly and start taking advantage of the screen lock.
I highly recommend this game, and I think it's worth every minute you play. Even when I got frustrated with the challenges, I found a real sense of accomplishment by overcoming them. A handful of glitches got in the way of two challenges, but they weren't game-breaking, and they're not universal (you probably won't experience them unless you play the same way I do). But all in all, I couldn't stop smiling and bouncing in my chair while I exclaimed with each revelation that "I love this game!"