Thank you for playing my game. I'm glad you enjoyed it.
The glitch with the upgrade tooltip has been fixed. Also, the camera zooming in the opposite direction of what is intuitive was also a glitch and has been fixed. I have incorporated your suggestions about the middle click keeping the cursor where it is and swapping sides for player/enemy information. Thank you for the suggestions.
My goal was not for the player to buy all 4 upgrades in most situations. In recent testing I also felt there was not enough reason to pass on buying an upgrade unless it was had anti-synergy with current upgrades. My current plan is to double the cost of upgrades and make them much stronger. I haven't committed to that plan yet though.