Xlox Walkthrough Part 1 Levels from 1 to 21 Cool Math Games 

The goal of the game is to remove the game board all the squares. To do this, you just need to click on these squares, if there is another cube horizontally or vertically, then it will disappear, if not, then it will appear. It is necessary to use the level structure to make such figures, which destroy themselves. In this video is walkthrouh for Xlox game from 1 to 21 level.
The game is taken from the site Cool Math Games.