diff --git a/utils/gr-sim/twister/Makefile b/utils/gr-sim/twister/Makefile
new file mode 100644
index 00000000..c9649307
--- /dev/null
+++ b/utils/gr-sim/twister/Makefile
@@ -0,0 +1,32 @@
+CC = gcc
+CFLAGS = -O2 -Wall -g
+LFLAGS = -lm
+
+SDL_LIBS= `sdl-config --libs`
+SDL_INCLUDE= `sdl-config --cflags`
+
+all:	generate_sines \
+	twist_6502
+
+###
+
+generate_sines:	generate_sines.o
+	$(CC) -o generate_sines generate_sines.o $(LFLAGS) -lm
+
+generate_sines.o:	generate_sines.c
+	$(CC) $(CFLAGS) -c generate_sines.c
+
+###
+
+twist_6502:	twist_6502.o ../gr-sim.a
+	$(CC) -o twist_6502 twist_6502.o ../gr-sim.a $(LFLAGS) $(SDL_LIBS)
+
+twist_6502.o:	twist_6502.c
+	$(CC) $(CFLAGS) $(SDL_INCLUDE) -c twist_6502.c
+
+
+
+###
+
+clean:	
+	rm -f *~ *.o dots dots_dump dots_play dots_minimal dots_6502 dots_play2
diff --git a/utils/gr-sim/twister/twist_6502.c b/utils/gr-sim/twister/twist_6502.c
new file mode 100644
index 00000000..e76f201e
--- /dev/null
+++ b/utils/gr-sim/twister/twist_6502.c
@@ -0,0 +1,80 @@
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <malloc.h>
+#include <math.h>
+
+#include "../gr-sim.h"
+#include "../tfv_zp.h"
+
+int main(int argc,char **argv) {
+
+	int ch,y,j;
+	double pi=3.14,f,e,m,n,s,t,q,r;
+	double a[64*48],b[64*48];
+
+	grsim_init();
+
+	gr();
+
+	j=0;
+	for(e=0;e<pi*2.0;e+=0.1) {
+		m=15.0+cos(e)*12.0;
+		n=pi-sin(e)*pi;
+		for(y=0;y<48;y++) {
+			f=(double)y*0.5/m-n;
+			a[j]=8.0*cos(f);
+			b[j]=8.0*sin(f);
+			j++;
+		}
+	}
+
+
+
+	clear_screens();
+	soft_switch(MIXCLR);
+
+	ram[DRAW_PAGE]=0;
+
+	while(1) {
+	j=0;
+	for(e=1;e<63;e++) {
+		for(y=0;y<48;y++) {
+			s=20-a[j];
+			t=20-b[j];
+			q=20+a[j];
+			r=20+b[j];
+
+			/* re-draw background */
+			color_equals(0);
+			hlin(0,12,27,y);
+
+			color_equals(1);
+			m=s; n=t;
+			if (q<r) { m=q; n=r;}
+			hlin(0,m,n,y);
+
+			color_equals(2);
+			if (r<s) { t=r; q=s;}
+			hlin(0,t,q,y);
+
+			j++;
+
+		}
+		grsim_update();
+
+		/* approximate 50Hz sleep */
+//		usleep(20000);
+		usleep(40000);
+
+		ch=grsim_input();
+		if (ch==27) {
+			return 0;
+		}
+	}
+
+	}
+
+	return 0;
+}