Nice game, really fun gameplay. I have all the badges and the survival one was one of the easiest if you ask me. I went from being at level 15 to 42 (stopped there) in one go.
I held both glades up for as long as I could and killed every spider, but then at level 37 I lost one of my glades which actually made the survival easier as I only had to protect one then. So just kill all spiders and protect one glade, that's my advice.
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