VVVVVV is a retro styled 2D platformer by Terry Cavanagh, creator of dozens of free games. You play as the fearless leader of a team of dimension exploring scientists who inadvertently crash, and are separated. The game involves exploring the strange world you've found yourself in, and reuniting your friends. VVVVVV explores one simple game mechanic: you cannot jump - instead, you reverse your own gravity at the press of a button. The game focuses on playing with this mechanic in a variety of interesting ways. The game is designed not to artificially gate your progress. In VVVVVV there are no locks, no power-ups, no switches, nothing to stop you progressing except the challenges themselves.
VVVVVV is a masterpiece and one of the best platformers I've ever played, there are many acheivements and game modes / trials to keep you coming back to play more and more after you have completed the game itself and have gotten the tunes stuck in your head from the brilliant soundtrack that comes with it. There are lots of areas to discover and things to collect, there are also in-game "Trophies" to acquire too if you're feeling up to a tough challenge.
This game is brilliant for so many different reasons, one of the main reasons is because It has the ability to create a great atmosphere while using extremely simple graphics, said graphics are also one of the primary things that gives this game it's charm.
While it's a difficult game (but by no means impossible), it has a nice frequent checkpoint system that keeps you from losing too much progress at one given time, as it is likely that you will die a LOT on your first run. People who have posted negative reviews of this game by saying "It's too hard" are most likely just bad at it. The game is hard, yes, but it's not hard to the point where it takes hours to get through a certain area. The balance is just right, in my opinion.
Overall, a great game with a great soundtrack. Definitely add this one to your collection, whether it's on sale or not! I'm really glad I picked this up in the sale and took the time to try it. You won't regret it.