x_offset

[Graham]

Hi All,
I am just starting with Python/pygame and am playing around with shapes.
I am trying to get some lines on screen as below (not dotted)
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I can get the y_offset to work but not the x_offset what am I missing?

    for y_offset in range(0, 100, 10):
        for x_offset in range(0, 100, 10):
            pygame.draw.line(screen, RED, [x_offset, 160 + y_offset], [x_offset-10, 160 + y_offset], 5)

Thanks for looking