Why doesnt just connecting 2 inputs to the output work as an OR? seems fine to me and all the NAND looks more complicated for no reason 

Is it just code error?

In a real circuit, electricity should not flow from output to output. While it works in different types of software, physically it could cause issues. 

because if both of the inputs are not the same, it would try to get in a superposition that could show both. So it will be laggy and if you try to use it, it can crash your game.