This game is a riot! Very cute and a clever idea. Every time I picked up too many coins I made a puffing noise in real life just for giggles. I actually enjoyed the slow down mechanic, it made you have to plan your trips carefully through the dungeon to collect the coins/ avoid the ghost.
I do wish the ghost couldn't go through walls or at least that he maybe got slowed down a little by walls? Or maybe - you could have like a bait system to temporarily distract the ghost by throwing something? I know that he is a ghost and so walls shouldn't be a problem but it gave him a bit of an unfair advantage when I had to race around a section and he didn't.
All in all though - AWESOME. Nice job!