Considering this is your "first time making a platformer", there is an insane display of talent on display here. From the artwork to the sound design to the juice and game-feel, it's a really great snippet of enjoyment.
I think you're aware perhaps, but the gameplay I think can get fairly stale fairly quickly - considering how much love and attention went in to every other aspect of the package, I think it's completely understandable. Maybe if the game wasn't time based but rather you have to chase the rat after you find him that might have been better?
Don't take this nit-picking as criticism, however - you've done an amazing job and should be proud of it :)