I hate having max mass reduced. Sometimes I can get a powerful upgrade, but I buy a different one, and now I don't have enough max mass to get the powerful upgrade. Can you at least give a warning for what does it?
Minerals increase your Max Mass, so spending them also reduces the bonus they provide. It’s an intentional mechanic that encourages you to manage different resources depending on what you want to unlock. You can see the Max Mass bonus in the tooltip by hovering over either the Minerals resource or the Max Mass icon in the Stats section. That said, I agree that if you don’t hover over those elements, you may never realize how it works. I’ll try to make this mechanic much more obvious in the game.