The final volume in a series that combines logic puzzles and basic coding instruction with a mystery plot! The Coders always knew their programming skills would take them far, but they never guessed they would take them to another dimension! Or to be accurate, one dimension less—to save humanity, Hopper, Eni, and Josh must travel to Flatland, a dangerous two-dimensional world ruled by polygons. If they can return home safely with a turtle of light, they might just stand a chance in their final showdown with Dr. One-Zero!