Cool idea, the concept is unique and has real potential. Main feedback I would give is more tutorialisation, giving the player more information, e.g. where the goblin starts, and also it's really important to make the artstyle cohesive which can be done by ensuring all pixels are the same size and you stick to a colour palette.
(Also there was some lag when new objects spawned in for the first time, you can fix this by using PRELOAD instead of LOAD)