Hmm... this was kind of strange. I like the visuals and the general concept though. I think that it needs some tweaking, like for example:

-Make the enemies walk in paterns

-Make a countdown system to the "ghost phase"

-Add states to the enemies like "unsuspicious ", "suspicious", "aware"...

Overall I think it is a nice experience... Good Luck!

Unfortunately most of my playtime came down to just waiting for ghost form. It would have been nice to have more to do in between periods of invisibility.

Those are some great visuals! But I have to say, I didn't like the sound effects and they got really annoying. Gameplay-wise I think you have to explain your game better to the player. It took a moment for me to get the rules and I'm still not sure, if I really understood the mechanics, as in you can just walk by the first guard. Also the level exit could be a little bit more clear - after collecting the gems I didn't know where to go. And the exit button in the menu didn't seem to work.

Alternative tittle "Patience game", you need to be very patient until it's the right time to move or you lose.