Tags: Comedy, Adventure, Fantasy, Action, Mystery
(Credits go to Wikipedia for writing a really good plot)
Plot: Kaito, a puzzle loving freshman, is selected as a candidate for "Phi-Brain". He and his sister Nonoha find a "unsolvable puzzle" near their school. The puzzle turns out to be a "life-threatening "philosopher's puzzle" created by the mystery group P.O.G (Puzzle Of God). After successfully solving the puzzle, Kaito is designated as a Solver and is joined by other Solvers as they battle P.O.G all over the world by solving the "philosopher's puzzles".
My thoughts: I really like the anime. It's got everything that I'm looking for in a anime: humor, action, suspense....There are three seasons of Phi-Brain by the way.
Overall, it's a good anime and I recommend it. Also, feel free to discuss the anime, but make sure that if there is a spoiler to put it in spoiler tags. I don't want people who are about to watch the anime to be spoiled.