Mathematics made mouth-watering.      Things to Make and Do in the Fourth Dimension is an alternative math class. How can math help you choose a second-hand car? Why is a text message like a Sudoku? How much fun can you have with a barcode? Matt Parker explains that math is difficult because it's one of the few subjects that requires us to train our brains to think in an entirely new way, and to confront things with no direct analogy in everyday life--imaginary numbers, snowf