This is a neat take on the theme! I love how you basically just become the object you're trying to blend in with, and the fact that all of the levels are different scenarios.
That being said, with over 3 hours, I feel like the visual and audio departments were a little lacking. I'm not sure how much time you actually took to make the game, so I don't even know if this criticism is valid, but a single music loop would have worked.
You're very brave to make the game in JavaScript instead of a normal game engine. I applaud you!
The concept is great. Extra polish in execution would make it even better. Nice job!