This book presents advanced heuristics used in primary school Mathematics. Featuring 210 specially selected worked problems classified under 23 chapters, the author aims to introduce and demonstrate the power of various tools including the use of circle transformations, inverse ratios, distance diagrams and special geometrical properties among others. Problems going beyond the mainstream which require far more exquisite treatment such as special counting techniques (of grids, paths and shapes) and cryptarithms (typically taught to GEP and Math Olympiad students) are also examined. By grouping the questions on a conceptual basis, the essence of each type of model is thus illustrated in depth.