I've been watching the development of this game for a long time, and remember the first alpha demo. The game has come a huge way since then.
The basic principles are a lot like 'Portal'. For instance to complete the level there will be a bunch of challenges and puzzles in the way. Some will take time to complete, others you will get straight away.
To increase the longevity of the game there are hidden awards scattered through the levels. Many of these will be quite hard to miss, others however still elude me. Gaining these will unlock another game mode, called Challenge mode.
Each time you complete a level you get a rating. This encourages you to try and best your high score or just to try and beat your friends' scores.
There are also awards. Most of these are just for completing a stage. But they are all different and nice to look at.
The engine is well built and the levels load really quick. Even the larger levels load within a few seconds! The only down part is the built in MP3 player. But I'm sure this will soon be patched. The soundtracks how ever are really decent.
Searching up at the engine it is quite possible that the developers will release a multi player expansion (hopefully for free) as the engine supports online gaming.
I can also imagine that it would be quite easy for them to release new levels as the main game world (or main hub) seems to have space for new portals to allow it. It'd be nice if a level building set was released, but they are still young, and so they may release one after my review.
For only a fiva I can't give it any less that a 8/10 since I will be playing this for many more hours. The score would bump up with multi player and a level kit or SDK.
P.S. I thought that the installer had crashed on me, but if you leave it it sorts its self out and installs the game nicely.