story identification - Looking for title/author of young adult book like "Ender's Game" I read years back

Virtual War Chronologs by Gloria Skurzynski.

http://gloriabooks.com/virtual.html

Cool Science Fiction!
The Virtual War Chronologs:
Book 1

The story of Virtual War:

By the year 2080, plague, disease, and nuclear war have confined Earth's two million human survivors to a few domed cities, where they are governed by the Western Hemisphere Federation, the Eurasian Alliance, or the Pan Pacific Coalition. When it is discovered that a small group of islands in the Pacific has become livable again, the three federations decide to wage a bloodless virtual war, with the winner to take possession of the island called Nuku Hiva.

All his life Corgan, then fourteen, has trained to be the champion of the Western Federation. Genetically engineered for quick reflexes, superior physical condition, and a remarkable time-splitting ability, he's been raised in isolation inside a virtual reality Box..

Only three weeks before the start of the War, Corgan meets - virtually - his two teammates: Brig, a ten-year-old mutant who is a superb strategist, and Sharla, the same age as Corgan. It is Sharla, with her brilliant ability to break codes, who brings him his first real human contact.