Hard, but worth the effort.
I admit, when i first played this game i found it tough. I was immediately slaughtered by the bad guys. And I had trouble when i ran from cover to cover and tried to hide behind a box only to find i was not exactly in the right spot to take cover, was then discovered, and then had to restart the level.
But, once I got the hang of it i couldn't get enough. Teleporting around the bemused bad guys as they take cover and look for you in a metal gear solid type style really made me giggle. The bosses were plenty difficult, could have gone for more though, and that last boss, well, damn, took me nearly an hour to kill him.
What I really enjoyed about the game is that it is non linear in the sense of how you could accomplish the mission, sure you can kill all the bad guys in a huge fire fight, but you can also kill them with stealth, you can attack them and then hide and they will have trouble finding you, or you can have a mixture between sneaking around and killing them.
The weapons drop system was fantastic as well, it supplied the player with enough ammo to get the job done, but not enough to abuse the weapons you found.
I found myself cursing as i shot at a guy and he would take off running (another good addition by the way) to find some cover. Only to heal himself over time just as you could (by the way I love games where the main character is just as good as the bad guys, and it is the skill of the player to make him better.)
I applaud you, and say "Well done sir!"
I look forward to playing more games you make.