A very enjoyable game and includes some excellent dialogue that's chocked full of comedy and wit. Infact this game has the best wit I've encountered and had me laughing on numerous occasions.
Replayability: Possible to replay but unlikely as the puzzle solutions are now known.
It would have been nice if some puzzles had multiple solutions, so you could choose to either take the easy solution, or challenge yourself and try for the harder solution, and then offer a reward (or another level).
The story is unique and the cut sequences are interesting enough that you'll not want to skip them.
Each level is either a progression from the last, or an interum level that doesn't actually look like a level, however the whole game feels very consistent and each level complements the immersion that the game offers.
First Person View only.
Being a First Person View only you're vision does feel quite limited at times as you can't see what is available in the next room, or on a high platform. This will result in the fact that you will die a few times while you work out exactly what you have to do to solve the puzzle. Many levels include areas resulting in death. Such as water and bottomless pits.
Each level provides you with features that you must use in order to complete the test. These are all very interesting and unique and will allow you to circumvent large obstructions and give you the ability to jump large distances.
The range of unique things you can do in the game is great. I won't explain any of them here because it's more interesting to discover them when you play the game. You can re-route objects, lasers and other items through any portal that you open. This is very cool fun.
The primary thing you will be doing is opening portals that will allow you to move from one section to another section instantly. This is a cool idea.
One thing that is worth pointing out, is that there is no falling damage. Woohoo. This means you can fall from great distances and not die. Infact many of the puzzles require that you can do this in order to complete the challenge.
Creating portals can result in a conundrum because you will be able to look at yourself entering or existing the other portal through the portal. Looks kind of weird, especially when you do that and find out you're a girl.
Using portals is great however it will also change your perspective. You will be turned around, rotated or inverted as you exit a portal, this can cause you disorientation especially if you need to do something (such as open another portal) the instant you leave the existing portal. You will often find yourself exiting the portal facing the wrong way, so you may find that a few sequences you will have to complete numerous times until you work out which direction you have to turn, the instant you exit the current portal.
It would be good if you could turn a portal off. Once you open a portal you can not close it. You can only relocate it somewhere else. It would have been nice that if you open a blue portal that you could click to open another blue portal where the current blue portal exists in order to turn it off.
The Official Testing Chamber. Here is where you have the most amount of information available to you. Each chamber provides you with an information chart as to what options are available for you to use. In the chamber you will see markings to help you indicate what you need to do and where the exit is.
Behind the Scenes Sections. In many instances you will be taken behind the scenes of the facility where the testing is conducted and you need to navigate your way either to the next testing chamber, or to the next game sequence. These areas will offer you the most challenge because nothing is sign posted. There is rarely a clear exit marked, and if there is, it is usually almost out of your vision, so you have to progress part way into the level before it becomes visible. I found these sections of the game very enjoyable.
There is no in game map, no journal, no pda, no inventory and no ability to upgrade your character, or the portal gun. Not that any of these items are really needed in this style of game.
You can save anytime you want and it is honored. It is not a checkpoint saving game, however it does autosave numerous times for you, such as each time you complete a task, or each time you enter a new level.
The dialogue from the robot is funny, witty and generally interesting to listen to, however some times the robot is talking while you can continue to walk to another room, making the dialogue virtually impossible to hear. This caused me to backtrack to where the robot was until it completed whatever task it was trying to complete, so I could hear all the dialogue, then I moved forward to complete my task. Only a small issue, but none the less when the dialogue is this interesting and clearly they have spent quite a bit of effort making it, that it is a shame if you miss out on some of it.
You have no weapons, however you can redirect other things in certain levels to allow you to damage the environment.
Maybe what the game could have done was allow multiple solutions to the puzzle. Highlight this in the test chamber introduction screen so that you can choose the easy or the hard option. Example: they could offer a player two cubes on easy mode, and only one on hard mode, making you work out a solution that has to reuse a cube.
Then if you solve the puzzle using the hard solution, be offered another puzzle as a reward. That way, the harder you play the more reward you get.
The game even offers you additional configuration options for handling the mouse and cursor acceleration
*update* Apparently there are additional areas that you can explore, which initially I didn't consider to contain a reward, other than you may experience some additional dialogue
There were a few funny signs around the place, but I didn't consider that enough to warrant a higher score.