Stealth without killing or open fight with machine gun - all of this is valid measure. There is freedom to walk around but also boundaries which makes game world real.
There are no unnecessary locations, spaces for the sake of spaces. The best way to make open world as I believe. It makes it easy to believe in this environment, unlike other fantastic worlds which were made from scratch. It is really looks like possible future when there are something new but also something old is there with us. Magnificent mix between european architecture and futuristic style of everything else. Also it is very often that mission continues further and appears in the next part of the game.
All missions are connected with the main story somehow and really exiting itself. It is not ordinary mission about collect/fetch/craft/beat and etc. Intrigue story about spies and crime investigations is very tense.
