diff --git a/include/gint/drivers/r61524.h b/include/gint/drivers/r61524.h
index ff2d1b5..71510c8 100644
--- a/include/gint/drivers/r61524.h
+++ b/include/gint/drivers/r61524.h
@@ -55,6 +55,12 @@ void r61524_display_rect(uint16_t *vram, int xmin, int xmax, int ymin,
    TODO: Make that a video mode. */
 void r61524_display_mono_128x64(uint32_t *vram);
 
+/* r61524_display_mono_128x64(): Display a gray-style VRAM
+   This experimental function updates the display with the contents of a 128x64
+   gray VRAM pair, used with the fxg3a compilation target.
+   TODO: Make that a video mode. */
+void r61524_display_gray_128x64(uint32_t *light, uint32_t *dark);
+
 /* r61524_start_frame(): Prepare the display for a region update
 
    This function sets up the display driver to receive graphics data to update
diff --git a/src/gray/engine.c b/src/gray/engine.c
index ccb6f53..c5cc857 100644
--- a/src/gray/engine.c
+++ b/src/gray/engine.c
@@ -14,8 +14,12 @@
 #include "../render/render.h"
 #include <gint/config.h>
 
-// TODO: Move the gray "engine" into the T6K11 driver.
-#if GINT_RENDER_MONO && GINT_HW_FX
+#if GINT_HW_CG
+#include <gint/drivers/r61524.h>
+#endif
+
+// TODO: Move the gray "engine" part into the T6K11 driver.
+#if GINT_RENDER_MONO
 
 /* Three additional video RAMS, allocated statically if --static-gray was set
    at configure time, or with malloc() otherwise. */
@@ -26,6 +30,8 @@ GBSS static uint32_t gvrams[3][256];
 /* Four VRAMs: two to draw and two to display */
 static uint32_t *vrams[4] = { NULL, NULL, NULL, NULL };
 
+#if GINT_HW_FX
+
 /* Current VRAM pair used for drawing; the value can either be 0 (draws to
    VRAMs 0 and 1) or 2 (draws to VRAMs 2 and 3). */
 static int volatile st = 0;
@@ -40,6 +46,10 @@ static int runs = 0;
 /* Delays of the light and dark frames for the above setting */
 GBSS static int delays[2];
 
+static int gray_int(void);
+
+#endif
+
 /* The alternate rendering mode structure used to override d*() */
 static struct rendering_mode const gray_mode = {
 	.dupdate      = gupdate,
@@ -68,13 +78,16 @@ static struct rendering_mode const gray_exit_mode = {
 //	Engine control (init/quit and start/stop)
 //---
 
-static int gray_int(void);
 static void gray_quit(void);
 
 /* gray_isinit(): Check whether the engine is initialized and ready to run */
 static int gray_isinit(void)
 {
-	return (vrams[0] && vrams[1] && vrams[2] && vrams[3] && timer >= 0);
+	return (vrams[0] && vrams[1] && vrams[2] && vrams[3]
+#if GINT_HW_FX
+		&& timer >= 0
+#endif
+		);
 }
 
 /* gray_init(): Initialize the engine
@@ -95,6 +108,7 @@ GCONSTRUCTOR static void gray_init(void)
 	vrams[3] = malloc(1024);
 	#endif /* GINT_STATIC_GRAY */
 
+#if GINT_HW_FX
 	/* Default delays from Graph 35+E II are different from other models */
 	if(gint[HWCALC] == HWCALC_G35PE2)
 	{
@@ -110,6 +124,7 @@ GCONSTRUCTOR static void gray_init(void)
 	/* Try to obtain the timer right away */
 	timer = timer_configure(GRAY_TIMER | GRAY_CLOCK, 1000,
 		GINT_CALL(gray_int));
+#endif
 
 	/* On failure, release the resources that we obtained */
 	if(!gray_isinit()) gray_quit();
@@ -128,10 +143,13 @@ GDESTRUCTOR static void gray_quit(void)
 	vrams[3] = NULL;
 	#endif /* GINT_STATIC_GRAY */
 
+#if GINT_HW_FX
 	if(timer >= 0) timer_stop(timer);
 	timer = -1;
+#endif
 }
 
+#if GINT_HW_FX
 /* gray_start(): Start the gray engine */
 static void gray_start(void)
 {
@@ -148,6 +166,7 @@ static void gray_stop(void)
 	runs = 0;
 	st = 0;
 }
+#endif
 
 //---
 //	Dynamic udpate and rendering mode
@@ -201,6 +220,7 @@ int dgray(int mode)
 	return 0;
 }
 
+#if GINT_HW_FX
 /* gray_int(): Interrupt handler */
 int gray_int(void)
 {
@@ -232,6 +252,19 @@ int gupdate(void)
 	st ^= 2;
 	return 0;
 }
+#elif GINT_HW_CG
+int gupdate(void)
+{
+	if(dmode == &gray_exit_mode)
+	{
+		dmode = NULL;
+		return 1;
+	}
+
+	r61524_display_gray_128x64(vrams[0], vrams[1]);
+	return 0;
+}
+#endif
 
 //---
 //	Query and configuration functions
@@ -243,6 +276,7 @@ int dgray_enabled(void)
 	return (dmode == &gray_mode);
 }
 
+#if GINT_HW_FX
 /* dgray_setdelays(): Set the gray engine delays */
 void dgray_setdelays(uint32_t light, uint32_t dark)
 {
@@ -274,5 +308,12 @@ void dgray_getscreen(uint32_t **light, uint32_t **dark)
 	if(light) *light = vrams[base & 2];
 	if(dark) *dark = vrams[base | 1];
 }
+#elif GINT_HW_CG
+void dgray_getvram(uint32_t **light, uint32_t **dark)
+{
+	*light = vrams[0];
+	*dark = vrams[1];
+}
+#endif
 
 #endif /* GINT_RENDER_MONO && GINT_HW_FX */
diff --git a/src/r61524/r61524.c b/src/r61524/r61524.c
index e5adac4..2e256d8 100644
--- a/src/r61524/r61524.c
+++ b/src/r61524/r61524.c
@@ -238,12 +238,13 @@ void r61524_display_mono_128x64(uint32_t *vram)
 		write(border);
 }
 
-void r61524_display_gray_128x64(uint32_t *vram)
+void r61524_display_gray_128x64(uint32_t *light, uint32_t *dark)
 {
 	dma_transfer_wait(0);
 	r61524_start_frame(0, 395, 0, 223);
 
 	int border = 0xe71c; /* C_RGB(28, 28, 28) */
+	int colors[] = { 0x0000, 0x528a, 0xad55, 0xffff };
 
 	for(int i = 0; i < 16 * 396; i++)
 		write(border);
@@ -256,11 +257,13 @@ void r61524_display_gray_128x64(uint32_t *vram)
 
 			/* longword-x position */
 			for(int lwx = 0; lwx < 4; lwx++) {
-				int32_t i = vram[lwx];
+				int32_t il = light[lwx];
+				int32_t id = dark[lwx];
 				/* sub-x position */
 				for(int sx = 0; sx < 32; sx++) {
-					int color = ~(i >> 31);
-					i <<= 1;
+					int color = colors[(id >= 0) * 2 + (il >= 0)];
+					il <<= 1;
+					id <<= 1;
 					write(color);
 					write(color);
 					write(color);
@@ -270,7 +273,8 @@ void r61524_display_gray_128x64(uint32_t *vram)
 			for(int i = 0; i < 6; i++)
 				write(border);
 		}
-		vram += 4;
+		light += 4;
+		dark += 4;
 	}
 
 	for(int i = 0; i < 16 * 396; i++)