Spent 11,250 on an upgrade.. it takes bloops and .. NO UPGRADE.. well.. i've been grinding uselessly for too long now.. no more of this grindfest for me.
I think i can speak for A LOT of people when i say there should be an option to sell your upgrades. especially since everything is so expensive. it gets to the point where trying to upgrade several diferent skills for each slot is pointless as you can NEVER afford so many.
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 "Bloons Super Monkey 2"){kind=icon}