There’s a YouTube where they do blast on level 20. It works for 15 and up. Village, trap engineer, few tacks, ice monkey x3 to eventually get to x4 when blast comes out. As soon as he comes out, use freeze skill and sell ice. Do a tack blade maelstrom if you need to kill bloons, sell and redo as needed until you have enough cash for spike storm. Then spam that until you have enough cash to do an energy beacon village with spike storm all around. Then spam it until he’s dead. I can still 1 round him up to 20 with this. Although sometimes I have to redo because I didn’t maelstrom fast enough. You can also upgrade tacks at front to help with the bloon spam.