Here is the result of my first few hours of work. (I'm afraid I'll only really have this weekend to work on it but wanted to see what I could do anyway.)
You play as a vampire who has no reflection but is able to switch at will between reality and the reflected world. Through stealth platforming and puzzle solving using the dual-world mechanic you must satisfy your blood lust. Some objects, like yourself, have no reflection whilst other exist only in the reflected world. At this stage I've put together this basic mechanic along with some initial pixel art work.