One of the best story-based single player FPS ever made!
I had some preconception about this game. I was excited and a bit terrified when waiting. When I got into the game the excitement is still going strong and the terror only surfaced when I met spiders! FOR THE LOVE OF GOD, THE SPIDERS! :D Comedy aside, this game is great. It rewards the player enough, combat is challenging enough and the puzzles are extremely well done. I'm currently on fifth level and I have no clue about how to open the door with the golden lock right at the end of level 3. I'm sure I didn't do all of level 4's puzzles neither...and boy those puzzles left me a good old-fashioned feeling :)