Blue orbs should render over power orbs. The doors can be open through the buy menu if they over lap. Still dont know what blue orbs need to be placed i just buy one for each orb. Love the new items would be nice if the upgrades said what they do before you buy them
Global Balls don't need to be placed anywhere specific. They just affect all power balls. The more you have, the quicker and more effective power balls are.
