Nice entry! I always love it when a game pulls a "Would you kindly..." and guilts you for playing it!
As a prototype this is fun, but I think it could use a little more work to be enjoyable.
1. Movement isn't normalized, so moving diagonally is twice as effective as move in a cardinal direction.
2. Increasing movement speed near death was a nice touch and it would have been nice to see this happen whenever you attempt to feed. This would also have the added benefit of making it easier to hunt down those pesky blood sacks and make the bloodloss when using this ability seem like a fair trade off.
3. Bloodloss in general didn't seem balanced. It never seemed like I gained enough blood from feeding to actually sustain my health (but maybe that was the point?)
4. Having no means of dealing with enemies was some what frustrating and they always seemed to catch up to you unless you moved diagonally (intentional?)
5. Great presentation and writing! This is the strongest part of the game. It's clear you put a lot of effort into it. Extra kudos for the multiple control options.