diff --git a/ubb-vga/ubb-vga2.c b/ubb-vga/ubb-vga2.c
index 11d41bc..429b8de 100644
--- a/ubb-vga/ubb-vga2.c
+++ b/ubb-vga/ubb-vga2.c
@@ -37,8 +37,13 @@
 #include "ubb-vga.h"
 
 
+#define	XRES	640
+#define	YRES	480
+
+
 static int bad;
 
+
 /* ----- I/O pin assignment ------------------------------------------------ */
 
 
@@ -231,7 +236,7 @@ static void until(uint16_t cycles)
 /* ----- Frame buffer output ----------------------------------------------- */
 
 
-static int line_words = 640/8;
+static int line_words = XRES/8;
 //static int line_cycles = US(36); /* nominally 31.77 us, but we're too slow  */
 //static int line_cycles = US(32); /* nominally 31.77 us, but we're too slow  */
 static int line_cycles = US(29.6); /* nominally 31.77 us, but we're too fast */
@@ -379,7 +384,7 @@ static void frame(const uint32_t *f)
 	*pddats = HSYNC;
 	until(line_cycles-US(0.79));
 
-	for (p = f; p != f+480*line_words; p += line_words)
+	for (p = f; p != f+YRES*line_words; p += line_words)
 		line(p, p+line_words);
 
 	/* Back porch */
@@ -392,12 +397,12 @@ static void frame(const uint32_t *f)
 
 static void session(void (*gen)(void *fb, int xres, int yres), int frames)
 {
-	uint32_t f[2*240*(line_words+1)];
+	uint32_t f[YRES*(line_words+1)];
 	int i;
 
 	memset(f, 0, sizeof(f));
 	ccube_init();
-	gen(f, 640, 480);
+	gen(f, XRES, YRES);
 
 	disable_interrupts();