Nice work! Great use of a shield as your weapon and invincibility. Though I think it would better if you could control the direction of your shield, the spinning is a bit hard to manage.
If you do plan to continue working on this, I have a few recommendations:
- Separate button inputs for clicking power ups and holding the shield. That way the user can keeping holding down the shield after clicking an upgrade.
- I think you should add some sort of feature that prevents players from camping in corners.
- Add cool visual effects for destroying things!