Very good prototype with a simple gameplay loop that is easy to learn! The rules could use some clarification, for example: When are the NPCs going to detect blood? Stealth games often have a visible indication of the enemies range of sight (as TheWorldsCutestGamer already mentioned). That would be a very helpful feature. Personally I would also add a little more time to battery life and faster charge speed, since waiting for battery charging wasn't a really engaging or fun part of the game. Still all in all fun to play and challenging level design.