Some things need fixed
The re-appears are blocky and you can just get stuck. It makes the action look terrible. Try a flashing re-appear, where (as like other games) the character appears but will flash a different color for a small amount of time during which he cannot be harmed; to even out the effect you could prevent the character from firing during that re-appear sequence.
During the Stage 8 intro there was ActionScript button text.
It didn't seem that the gauges for the power pick-ups were working properly.
You could implement a scoring system. Points for each Frownie killed, vary by type & ordered by difficulty, plus bonus points for defeating all of the Frownies. Plus, you could make a timing system by making the next wave of Frownies appear a set amount of time after the all of the Frownies in the current wave are defeated.
There are 3 lives for the game, but I think an interesting model would be 3 lives per stage where you have a life gauge and if your health is depleted you reappear flashing. Do that 3 times and you have to continue. Also, if all of the presents are stolen you have to continue. Along with all of this you would get 3 continues.
With that last part new Frownies with special abilities would be interesting.
And of course it needs sound.
Keep working on it.