A method and computer software are provided for making number place puzzles. Numbers and unknown are represented by variables that are assigned values such as in a plurality of nested loops. Instructions within each loop limit access to embedded loops until all assigned values form a valid solution. When some of the variables are pre-assigned values to create a number place puzzle, the output will be all valid solutions, if any. Multiple solutions provide information that assists in modifying the pre-assigned values to obtain a single solution.