private int screenToTile(int x, int bound) {
        //convert x/y coordinate into a tile coordinate

        //if x is negative, make them one tile's width lower
        //this is because the next step uses integer division, which
        //rounds down to lowest ABSOLUTE value and not lowest ACTUAL value
        if(x < 0)
        {
            x-= model.world.GRID_SIZE;
        }

        //convert from xy on screen to tile xy
        return ((x/model.world.GRID_SIZE)+bound)%bound;
    }