Cannot implicitly convert type `float' to `int

where is the int ?

    public float[,] board;
	public float GridHeight;
	public float GridWidth;

The error is here

   board = new float[GridWidth,GridHeight]

You are trying to create an Array with a float size, can you imagine an array sized “2.36666”? It is just not possible.

public float[,] board;
public int GridHeight;
public int GridWidth;

Just changing GridHeight and GridWidth to INT will solve it.