diff --git a/graphics/gr/rotozoom/rotate_simple.s b/graphics/gr/rotozoom/rotate_simple.s
new file mode 100644
index 00000000..6b1d31b2
--- /dev/null
+++ b/graphics/gr/rotozoom/rotate_simple.s
@@ -0,0 +1,240 @@
+	; ANGLE in our case it's 0..15?
+
+CAL	= $B0
+CAH	= $B1
+SAL	= $B2
+SAH	= $B3
+YPL	= $B4
+YPH	= $B5
+XPL	= $B6
+XPH	= $B7
+;YY
+;XX
+CCAL	= $B8
+CCAH	= $B9
+CSAL	= $BA
+CSAH	= $BB
+YCAL	= $BC
+YCAH	= $BD
+YSAL	= $BE
+YSAH	= $BF
+
+rotozoom:
+
+	; ca = cos(theta)*scale;
+	;      ca=fixed_sin[(theta+4)&0xf]
+
+	lda	ANGLE							; 3
+	clc								; 2
+	adc	#4							; 2
+	and	#$f							; 2
+	asl								; 2
+	tay								; 2
+	lda	fixed_sin,Y	; load integer half			; 4
+	sta	CAH							; 3
+	lda	fixed_sin+1,Y	; load integer half			; 4
+	sta	CAL							; 3
+
+	; sa = sin(theta)*scale;
+
+	lda	ANGLE							; 3
+	asl								; 2
+	tay								; 2
+	lda	fixed_sin,Y	; load integer half			; 4
+	sta	SAH							; 3
+	lda	fixed_sin+1,Y	; load integer half			; 4
+	sta	SAL							; 3
+
+	; cca = -20*ca;
+	; csa = -20*sa;
+
+	lda	#0
+	sta	CCAL
+	sta	CCAH
+	sta	CSAL
+	sta	CSAH
+
+	ldx	#20
+mul20_loop:
+	sec
+	lda	CCAL
+	sbc	CAL
+	sta	CCAL
+	lda	CCAH
+	sbc	CAH
+	sta	CCAH
+
+	sec
+	lda	CSAL
+	sbc	SAL
+	sta	CSAL
+	lda	CSAH
+	sbc	SAH
+	sta	CSAH
+
+	dex
+	bne	mul20_loop
+
+
+	; yca=cca+ycenter;
+
+	lda	CCAL
+	sta	YCAL
+	clc
+	lda	CCAH
+	adc	#20
+	sta	YCAH
+
+	; ysa=csa+xcenter;
+
+	lda	CSAL
+	sta	YSAL
+	clc
+	lda	CSAH
+	adc	#20
+	sta	YSAH
+
+	; for(yy=0;yy<40;yy++) {
+
+	lda	#0
+	sta	YY
+rotozoom_yloop:
+
+	; xp=cca+ysa;
+	clc
+	lda	YSAL
+	adc	CCAL
+	sta	XPL
+	lda	YSAH
+	adc	CCAH
+	sta	XPH
+
+	; yp=yca-csa;
+
+	sec
+	lda	YCAL
+	sbc	CSAL
+	sta	YPL
+	lda	YCAH
+	sbc	CSAH
+	sta	YPH
+
+        ; for(xx=0;xx<40;xx++) {
+	lda	#0
+	sta	XX
+rotozoom_xloop:
+
+	; if ((xp<0) || (xp>39)) color=0;
+	; else if ((yp<0) || (yp>39)) color=0;
+	; else color=scrn_page(xp,yp,PAGE2);
+
+	lda	#0
+	ldx	XPH
+	bmi	rotozoom_set_color
+	cpx	#40
+	bcs	rotozoom_set_color
+	ldx	YPH
+	bmi	rotozoom_set_color
+	cpx	#40
+	bcs	rotozoom_set_color
+
+	; scrn(xp,yp)
+
+	lda	XPH
+	sta	XPOS
+	lda	YPH
+	sta	YPOS
+
+	jsr	scrn
+
+rotozoom_set_color:
+	; color_equals(color);
+	jsr	SETCOL
+
+	; plot(xx,yy);
+
+	lda	XX
+	sta	XPOS
+	lda	YY
+	sta	YPOS
+
+	jsr	plot
+
+	; xp=xp+ca;
+
+	clc
+	lda	CAL
+	adc	XPL
+	sta	XPL
+	lda	CAH
+	adc	XPH
+	sta	XPH
+
+	; yp=yp-sa;
+
+	sec
+	lda	YPL
+	sbc	SAL
+	sta	YPL
+	lda	YPH
+	sbc	SAH
+	sta	YPH
+
+
+rotozoom_end_xloop:
+	inc	XX
+	lda	XX
+	cmp	#40
+	bne	rotozoom_xloop
+
+	; yca+=ca;
+
+	clc
+	lda	YCAL
+	adc	CAL
+	sta	YCAL
+	lda	YCAH
+	adc	CAH
+	sta	YCAH
+
+	; ysa+=sa;
+
+	clc
+	lda	YSAL
+	adc	SAL
+	sta	YSAL
+	lda	YSAH
+	adc	SAH
+	sta	YSAH
+
+
+rotozoom_end_yloop:
+	inc	YY
+	lda	YY
+	cmp	#40
+	beq	done_rotozoom
+	jmp	rotozoom_yloop	; too far
+
+done_rotozoom:
+	rts
+
+
+
+fixed_sin:
+        .byte $00,$00 ;  0.000000=00.00
+        .byte $00,$61 ;  0.382683=00.61
+        .byte $00,$b5 ;  0.707107=00.b5
+        .byte $00,$ec ;  0.923880=00.ec
+        .byte $01,$00 ;  1.000000=01.00
+        .byte $00,$ec ;  0.923880=00.ec
+        .byte $00,$b5 ;  0.707107=00.b5
+        .byte $00,$61 ;  0.382683=00.61
+        .byte $00,$00 ;  0.000000=00.00
+        .byte $ff,$9f ; -0.382683=ff.9f
+        .byte $ff,$4b ; -0.707107=ff.4b
+        .byte $ff,$14 ; -0.923880=ff.14
+        .byte $ff,$00 ; -1.000000=ff.00
+        .byte $ff,$14 ; -0.923880=ff.14
+        .byte $ff,$4b ; -0.707107=ff.4b
+        .byte $ff,$9f ; -0.382683=ff.9f
+
diff --git a/graphics/gr/rotozoom/rotozoom.s b/graphics/gr/rotozoom/rotozoom.s
index 9c31b0d4..6b1d31b2 100644
--- a/graphics/gr/rotozoom/rotozoom.s
+++ b/graphics/gr/rotozoom/rotozoom.s
@@ -1,6 +1,5 @@
 	; ANGLE in our case it's 0..15?
 
-
 CAL	= $B0
 CAH	= $B1
 SAL	= $B2
@@ -55,11 +54,23 @@ rotozoom:
 	sta	CSAL
 	sta	CSAH
 
-
 	ldx	#20
 mul20_loop:
+	sec
+	lda	CCAL
+	sbc	CAL
+	sta	CCAL
+	lda	CCAH
+	sbc	CAH
+	sta	CCAH
 
-
+	sec
+	lda	CSAL
+	sbc	SAL
+	sta	CSAL
+	lda	CSAH
+	sbc	SAH
+	sta	CSAH
 
 	dex
 	bne	mul20_loop