Great game overall! The gameplay is solid, challenging, and compelling. Every action the player can take has good feedback, from the ignition of the cannon, to the taking of the damage. I especially enjoyed the easter egg insane mode! I think i got 49 kills in that one! Music, menus, and story all support the theme and a solid overall experience. My only feedback might be to indicate the destruction of the crab immediately somehow. I know they flip over when dead, but perhaps some slight coloration change or impact effect might ensure a quick understanding that "i hit it" and therefore can switch to another target.
I'd love to see more from this game! Upgrades to show cannon trajectory, a visible representation of our health in game (crumbling castle), the sky is the limit which is a good sign that there's a solid foundation to imagine possibilities from.
Excellent work, and congratulations on submitting!