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I read a book about 10 years ago about a teenage boy that is in a government program for genetically enhanced children in a post-apocalyptic world. He is training for a holographic battle game against other countries where the winner gets the last piece of uncontaminated land.
He meets his partners, a girl about his age and a young boy who is crippled but a genius.
I don't remember much more than that but I have been looking for it for years. This is NOT Ender's Game or anything from that series, I have checked.