I can't be the only one who just had to do all the ways to end it simultaneously? As in, trying to micromanage it so all the finishing times to sync up? ... I think I have OCD.
Just as a tip to people: a single laser can practically disable 2 creeper spawners, and one fully. It shoots the creeper instantly, and none of it ever even spreads anywhere.
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 "Creeper World: User Space"){kind=icon}