Neat game! It is really polished, it is simple, yet there is some advanced mechanics (like run-jumping taking you further than just jumping). Visuals are simple, but they aren't bad, author do have taste! And all of this animations (I mean UI), and goofy ghost "Boo" sound making me love it.
But I suggest you adding some ui tips for entering the door, I wasted like 1-2 minutes trying to figure out where sould I put that diamond.
Well done!