It was fun to play at first, but the background(especially on the title screen)made my eyes hurt. I also didn't really feel like it fit the topic that well either as there's no consequence to alerting the guards and therefore it doesn't feel like a "fail"
If you decide to spend more time on this, I would suggest having some kind of counter to know how many guards have been alerted, and possibly have alerted guards chase after you, giving players a risk/reward system for waking more guards