The objective of the game is to complete a puzzle by converting one unit to another specified unit. The game is similar to a crossword puzzle except that the words are replaced with numbers.
The player must fill each white squares with the correct numbers (one number per square). These numbers can be written either from left to right or from top to bottom. The questions on the puzzle can be either a simple conversion or a conversion that involves an arithmetic operation.
There are 10 available cross-number puzzles. See Preview for example of the puzzles.