gah! How to clip rotated rectangles.

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tonyg

It shouldn't be this hard ;-)

Maybe it isn't.
Obviously the 'easy' answer would be the Viewport commands but if you have reason not to trust them you won't be using the 'easiest' method.
Anyway, I am, not suggesting doing a full-screen grab but, instead, have a screen-size image with a transparent centre.
Draw this image after all other drawing.
Alternatively, if the size of the border is to change then drawrect the border.

Graphics 800,600
While Not KeyHit(KEY_ESCAPE)
	Cls
	SetColor 255,255,255
	SetRotation 0
	DrawOval 100,100,30,100
	SetRotation 45
	DrawOval 150,300,30,100
	SetRotation 0
	drawborder
	Flip
Wend
Function drawborder()
	SetColor 255,0,0
	DrawRect 0,0,600,100
	DrawRect 0,0,100,600
	DrawRect 500,0,100,600
	DrawRect 0,500,600,100
End Function