Cool game. Gameplay was fun for the most part. But you had to know what to do as soon as you came into the game or else you'd be swarmed too quickly by enemies. The graphics are quite good for the jam, especially the enemies and the gun. If you want to make it a bit better, you could add an outline for the bar when mining the gold and an outline for the player himself (darkest color in your palette). The ending wasn't that satisfying, you could do a different drawing or animation of the aliens all dying once you got 100 gold, to fit your story. The code itself was good, I didn't run into any bugs. Overall, nice work!