**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**.