You can be risky with illumina and come to the edge. He will simply rocket jump to you and fall off the edge. You can also stay behind the hill and spam sword, when darkheart teleports to you he will just fall the edge aswell
Btw just use the tower strat then if ur on the floor under top then u can just drop bombs away on wave 6 as long as u stay at the end darkheart just falls off
slingshot is actually very OP, i just dug myself in very small gap between the wall and mountain, then i used it to kill rocketeers that managed to reach me. For some reason slingshot damages not with balls but in a zone between you and the point where your cursor is, and obstacles doesnt matter. I couldnt reach everyone but it wasnt needed because new wave starts after long time if all enemies wasnt killed, in the last wave dark and white brickbattlers got pushed by their teammates and fell in the void, then i jumped out of that gap and rushed to portal dodging rockets. So thats how i got it
Sling shot not is actually one of the best you can camp the hill and spam it and its hitbox is big even tho its slow it works until like wave 5 and 6 But this was actually reay helpful because i beat every round until wave 5
Stay on the tower and spam bombs on enemys also dodge rockets with sword once you reach wave 6 go behind the hill and be careful of the illumina because it might come spam your sword for when darkheart to to u then it falls after build up with trowel and place a bomb and be really close to it and being at the place wherethe tower is to travel there without dying then do strat again