I think this is my favourite entry so far. It´s adorable, the mechanics are nice, the graphics are good, the puzzles are interesting and everything´s very polished. I love how you used signs to give theinstructions but they also doubled as check-points and reset points for the levels! And you even designed the levels so they worked when teh player restarted from the checkpoint, even though they were on different places from where he enters the level at first! My hat´s off to you!
One small nitpick is that SPACE+WASD isn´t a very comfortable combination for me, if you develop this any further (you shoudl!) consider adding configurable controls or using the arrow jeys instead of WASD or something.
In the last screen before the chest I broke the stones from below, but as I was pressing UP and mashing SPACE I pushed the rock upwards to the corner. Somehow I manage to push the rock to the right, enter the previous level, reset it and get back to the final challenge, but maybe you should add something to prevent this from happening or add a checkpoint in that last screen. For a moment I thought I was stuck.
Awesome job, loved it!