this is a greaty game 4/5. a couple of things you could do to improve are, as many others have pointed out, the gaurds are pretty stupid. You could also put multiple targets on some levels. It would defintily be pretty cool if oyu could climb over some of the crates, so the gaurds cant see you. I am also not a fan of the "ultimate" acheivement as 30 second is too fast, assassins are paceint and wait for the right time. However if you did want to make speed a factor perhaps some missions could have another assassin that you have to compeat with to get the kill first. just a few ideas
it would be good if in addition to a time limit for the whole game there was also a limit of 1 minute for each move to prevent people from just letting the timer run out so you give up
The gaurds can only see a certain distance normally but yet as soon as the alarm goes off they can see you well enough to shoot you at twice that distance; that doesnt really make sense.
Im normally not a fan of RPG type game such as this one, however the fast pace driven by autoattack makes this game very enjoyable. I also enjoyed the realativly simple upgrade/equipment system.
In the next one a fixed position for all the extraction points would be good, although i like that the guards are somewhat random. It would also be cool if some levels had different settings instead of always a warehouse. For example forest or office building, ect.
the next one should be longer and more difficult, as well i would like to see a more comprehensive skill tree where the weaker upgrades lead to getting the more powerful abilities.