O(N^2) collision checks

[reinismu]

I'm checking move_all_players and it really bugs me that it is O(N^2). This wont work for real MMO.

Should really have a kd-tree index that allows to get closest entities in efficient way

[bfops]

Thank you for filing this @reinismu! Blackholio is intended more as a quick proof-of-concept project than a demonstration of best practices for a large-scale MMO.

We are planning to create more "best practices" code samples for various game systems, including collision physics, soon.