Part 2 (Cool Math Vesrions) is here:
You find yourself in a strange place where people once lived. Now it is abandoned and there is no one there. Earlier in the same place was your brother, who then disappeared. You can try to find him following him through the doors that lead to other worlds. The game has puzzles, but they are not complicated. You usually need to find something and use it in the right place. In this part of the game, we go through only one world and find the key to another world. Game taken from cool math games.