Collision solving

As of game version of 1.4.0 and higher, this collision resolving is no longer used, as collision is resolved using path nodes (eighter there is a path node and you can walk there, or not....) ×

This focuses on the collision solving in the game.
Here will be described collision for all objects (circle / line / line segment / rectangle), how are they computed (mathematical solutions) and handled in game.
Before you read anything about collision resolving, make sure you read and understand infinitesimal numbers problem, which is vital for understanding why are results treated as they are, and why the old solution (the more complex one) was not used in the end...
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