Dang, Santa means business! What exactly is he putting in those presents? XD
Fun little game! Works reasonably well, plus the mechanics and objectives are clear.
It might be helpful to have more visual feedback on the alien spaceship. I hit it many times and I couldn't tell if it was taking damage or not. Eventually I was dropped back to the start screen. Since my health was full, I'm assuming the game ended because I won. You can use a win screen, or even a second or two of showing the spaceship dying to let the player know what happened.