Terra X consists of a rectangular or square grid divided into regions. The aim is to place a digit from 0 to 9 into each region so that regions with equal numbers cannot share an edge (they may touch each other diagonally). For each grid point where four regions meet, the sum of the digits in those regions must equal 10. (All these grid points are marked with a small black dot.)
Cross+A can solve puzzles from 3 x 3 to 30 x 30.
Terra XV: for each grid point where four regions meet, the digits in those four regions must sum up to 15.
Terra XX: the sum of the digits must be equal 20.
