Get the screen coordinate for the top-left corner of a tile.

def get_tile_location(self, x, y):
        """Get the screen coordinate for the top-left corner of a tile."""
        x1, y1 = self.origin
        x1 += self.BORDER + (self.BORDER + self.cell_width) * x
        y1 += self.BORDER + (self.BORDER + self.cell_height) * y
        return x1, y1