I liked the graphics and the music gave the game some personality. My mouse got a workout too! However, the gameplay is pretty simple and get repetitive quickly. While you don't have the towers, other parts of a tower defense game would be a good addition, such as upgrades and different attack types (bombs, slowing effects, big attack with long cool down). Obviously that's all stuff that would be easier with more than 48 hours though!
For this game as it is, maybe fewer enemies with higher health would be a more interesting challenge? As others have said, your attacks are strong enough that you can just focus on a choke point and kill the goblins faster than they can escape your aim. If your enemies had higher health, you would have to attack them throughout their travel along the path, meaning you would be forced to prioritize which enemies you attack more.