Cross Sums by X-Sums 98! - Version 1.0.0.6 Solve More-or-Less Weekly Cross Sums Puzzles with the X-Sums 98 Viewer! The weekly puzzles are Challengers, but the viewer also has twelve, built-in puzzles of varying difficulty. Cross Sums puzzles are similar to crossword puzzles except that numbers are used instead of words; digits instead of letters.