"Inverto" is a first person shooter-puzzler with physical puzzles and gravity manipulations. The game is the ideological successor of such games as "Prey" and "Portal" with platformer elements.
I remember giving this game a go some time ago, and I've tried it recently as well.
It has fluid and smooth movement, and is somewhat complex to beat. I know it took me a bit of time to figure out some areas.
The game also has very nice graphics, and does not lag too much on good quality even on lower end PCs.
The concept of the game is actually very nice, and the gameplay is done well.
Overall the game is a 9/10. Nearly nothing is wrong with this game, though sometimes I had problems in levels.
That's simply my own intelligence, I suppose.
Test the demo, guys, and if you like it, then get the full game.
Give this game your money, it's well worth it. And it's $4, you can't go wrong.