Really cool idea. I like the level design with having the different vents to fly through, really gives a whole new perspective to an otherwise simple layout.
It was sometimes to attach to humans/blood bags, but otherwise it worked very well.
I think you've put the wrong mouse controls for draining/giving blood in the description though, it took me a while to realize you suck blood with right click and give blood with left click.
Great job with the game, it was enjoyable and a unique take on the jam theme!