Wow, this was great! I really liked how you described the controls in the beginning of the game. I immediately knew how to play without any prior instructions.
I really like the atmosphere and the graphics (especially the walls/floor!). Music and sounds were great too, really added to the game.
The sneaking mechanic was fun too, I liked how I couldn't get seen in the shadows. The sounds alerting the guards made the game a bit harder than expected, but overall it was really fun. Great job!