Honestly for a first submission it's not too bad.
The Ability to swap between Rat and Bat Is actually kind of awesome especially when the Bat form drains blood to keep it going. Kind of a risk vs reward mechanic you have.
As for implementing the the limitation, I think you did a good job, having the vampirat (Clever name btw) shoot blood as either a bat or a rat to defeat the enemies was a good time. Although it does seem like when one dies they all kind of die? Regardless of where they were when they died.
AI seemed to just focus on walking to you regardless on where you were, like some just descended like they were floating when they should have been falling or just stood still in the air.
As well as the text showing your blood & health seemed to shake when in bat form, it was a bit distracting.
Other than that, I wish there was more of a level, seemed basic, but for your first submission, I think you did a good job! Keep it up!