Tips:
Order of Regular Upgrades you should get:
Sticky Shield - Static Shield - Max Energy Infuser / Shield Bounce together (Goes up to Level 10). By this time, you should probably be around Level 45. From here, just upgrade Upgrade Base / Energy Cell. Don't forget to heal after every round if you get hit.
Order of Bonus Upgrades you should get:
ANTIMATTER SHIELD (Once you get this, you've pretty much beaten the game) - Heatseekers - The Exploder
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