The stone snake crawls forward and meets various obstacles, control points and groups of small stones of different colors on its way.
After passing through the checkpoint the stone snake is painted in a different color.
The stone snake can consume small stones of the same color as itself.
If a stone snake consumes a stone of a different color, it loses part of its tail.
If a stone snake hits an obstacle, it loses part of its tail.
The stone snake will die if it does not have a tail and it stumbles upon an obstacle or consume a stone of a different color.