This is actually great!
Aside from the constant message "The piggy bank is under attack" I have nothing but praise.
It looks good, it sounds good, there's even a zoom out feature so that I can see where the enemies are coming from more easily. There's powerups at the end of each wave and a boss fight!
Though I'm not sure if it's possible to defend the piggy bank enough that the annihilator doesn't immediately crush it? It seemed to spawn in when I was doing badly rather than at a specific time. I fought it twice and I feel like the second time was on a different wave than the first, but maybe I'm misremembering. In any case, I'm glad I saved the day, even though the one job I had was failed.