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From: Richard Ashbery <basura@invalid.addr.uk>
Newsgroups: comp.sys.acorn.programmer
Subject: Rotating a Colour-Filled Square
Date: Tue, 12 Nov 2019 14:05:03 +0000 (GMT)
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Rotating a square can be done with

MODE 1920,1080,32
FOR theta = 0 TO 360 STEP 90
x = 1000 * SIN(RAD(theta+45))
y = 1000 * COS(RAD(theta+45))
IF theta = 0 MOVE 1920+x, 1080+y ELSE DRAW 1920+x, 1080+y
NEXT

By altering the angle theta+45 to theta+55 the square can be made to
rotate 10°. If I try something similar with a filled square using
'RECTANGLE FILL' or PLOT &65 I'm unable to rotate it. Has anyone got a
simple routine that rotates a colour filled square about the screen
centre?