The art style takes me back to the good old days of Atari 2600 (more 8 bit sound effects could have helped there!). Nice concept. I have a small gripe in that putting ladders needs to be very precise, and even one pixel of a block above can stop going up the ladder. Maybe you could give the poor skele-fellow a tiny nudge when they just hit the corner. I also would have made the speed a bit higher. As it stands now, things get a bit tedious.