My last puzzle for this set of flashbacks is Shape Sudoku. Shape Sudoku is near the top of my list of favourite Sudoku variants. I discovered this type in Mutant Sudoku by Wei-Hwa Huang and Thomas Snyder. The world needs more books like this! The pieces fit to spell out “24 HPC” on the grid. I’ve seen this particular puzzle in several instruction booklets long after 2011, sometimes unaccredited.
Shape Sudoku – Decide how each piece fit into the sudoku grid. Pieces can be rotated but not reflected. Then solve the sudoku in the usual manner.