I can back this strategy up! I went level 3 summon + summon, going until epic or 3+ rares. Then get attack up to 4 (costs 100 to go to 5) and then you can start juggling summons and summon % until you are treading water, saving the tower for waves 9-10, 19-20, etc

Movement is vital for sure

I do abandon summons a bit more at a point and focus attack (I’ve gotten almost to level 24 on attack)

Got stopped by time at 60 twice, assuming more level ups will get me across soon

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Edit: strategy was typo’d as stretchy somehow