Mathrax

Mathrax consists of a square grid. The goal is to fill in each cell with numbers from 1 to N, where N is the size of the puzzle's side. No number may appear twice in any row or column. Circles with additional conditions may be situated on intersections of lines inside the grid; a circle may contain:

• A number and a sign of mathematical operation (addition, subtraction, multiplication, division) - a number is a result of an operation execution with numbers in diagonally adjacent cells.
• A letter "E" ("even") - all numbers in four cells are even.
• A letter "O" ("odd") - all numbers in four cells are odd.

Cross+A can solve puzzles from 3 x 3 to 9 x 9.