The inclusion of a guard's field of vision is a small, but very cool feature!

I like that you were able to squeeze whole game in single page and your game definitely follows the theme. I haven't actually played this, but seems like things can quickly start to escalate out of intruders control.

What I like most about this is that you can play any genre of sneaky game from Fantasy (Thief) to modern (sneaking out from a bank heist or a museum job) to cyberpunk and far future.  Love it!

Cool design! It looks like there's a typo that refers to the Intruder as the Thief in the first paragraph of the Playing the Game section. Other than that, though, this is a really cool idea, and I really like the way the stealth system works!