diff --git a/main.c b/main.c
index 4aae709..714c26e 100644
--- a/main.c
+++ b/main.c
@@ -41,6 +41,102 @@
  * PD3             -> /LED
  */
 
+uint8_t sequence_chase(uint8_t old_value, uint8_t *dir, uint16_t mask)
+{
+    uint8_t value = old_value;
+
+    do {
+        value = (*dir) ? value +1 : value -1;
+        value &= 0x0F;
+
+        if (value == 0x00 || value == 0x0F) {
+            *dir = (value == 0x00);
+        }
+
+    } while (!((1<<value) & mask) || value == old_value);
+
+    return value;
+}
+
+uint16_t color_ramp(uint16_t value, uint8_t *color)
+{
+    uint8_t col1 = (value & 0xFF);
+    uint8_t col2 = 0xFF - col1;
+
+    switch (value >> 8) {
+        default:
+            value = 0x0000;
+            /* no break */
+
+        case 0: /* red: on, green: ramp up, blue: off */
+            color[0] = 0xFF;
+            color[1] = col1;
+            color[2] = 0x00;
+            break;
+
+        case 1: /* red: ramp down, green: on, blue:off */
+            color[0] = col2;
+            color[1] = 0xFF;
+            color[2] = 0x00;
+            break;
+
+        case 2: /* red: off, green: on, blue: ramp up */
+            color[0] = 0x00;
+            color[1] = 0xFF;
+            color[2] = col1;
+            break;
+
+        case 3: /* red: off, green: ramp down: blue: on */
+            color[0] = 0x00;
+            color[1] = col2;
+            color[2] = 0xFF;
+            break;
+
+        case 4: /* red: ramp up, green: off, blue: on */
+            color[0] = col1;
+            color[1] = 0x00;
+            color[2] = 0xFF;
+            break;
+
+        case 5: /* red: on, green: off, blue: ramp down */
+            color[0] = 0xFF;
+            color[1] = 0x00;
+            color[2] = col2;
+            break;
+    }
+
+    return value;
+}
+
+void color_add(uint8_t *color1, uint8_t *color2, uint8_t *output)
+{
+    uint8_t i;
+    for (i = 0; i < 3; i++) {
+        uint16_t tmp = color1[i] + color2[i];
+        output[i] = (tmp & 0xFF00) ? 0xFF : tmp;
+    }
+}
+
+void color_sub(uint8_t *color1, uint8_t *color2, uint8_t *output)
+{
+    uint8_t i;
+    for (i = 0; i < 3; i++) {
+        uint16_t tmp = color1[i] - color2[i];
+        output[i] = (tmp & 0xFF00) ? 0x00 : tmp;
+    }
+}
+
+void color_div(uint8_t *color, uint8_t div, uint8_t *output)
+{
+    uint8_t i;
+    for (i = 0; i < 3; i++) {
+        output[i] = color[i] / div;
+        if ((output[i] == 0) && (color[i] != 0)) {
+            output[i] = 0x01;
+        }
+    }
+}
+
 int main(void) __attribute__ ((noreturn));
 int main(void)
 {
@@ -64,76 +160,20 @@ int main(void)
     while (1) {
         mpm_check_transfer();
 
-#if 0
         /* wait for complete update */
         rgb_update(COLOR_MASK, 1);
 
-//         _delay_ms(100);
+        _delay_ms(1);
 
         step++;
         if (step == 16) {
             step = 0;
-
-            if (xdir) {
-                x++;
-                if (x == 0x05)
-                    x = 0x08;
-                else if (x == 0x0C)
-                    xdir = 0;
-
-            } else {
-                x--;
-                if (x == 0x00)
-                    xdir = 1;
-                else if (x == 0x07)
-                    x = 0x04;
-            }
+            x = sequence_chase(x, &xdir, 0x1F1F);
         }
 
-        uint8_t color[3];
-
-        ramp++;
-        switch (ramp >> 8) {
-            case 6:
-                ramp = 0x0000;
-                /* no break */
-
-            case 0: /* red: on, green: ramp up, blue: off */
-                color[0] = 0xFF;
-                color[1] = ramp & 0xFF;
-                color[2] = 0x00;
-                break;
-
-            case 1: /* red: ramp down, green: on, blue:off */
-                color[0] = 0xFF - (ramp & 0xFF);
-                color[1] = 0xFF;
-                color[2] = 0x00;
-                break;
-
-            case 2: /* red: off, green: on, blue: ramp up */
-                color[0] = 0x00;
-                color[1] = 0xFF;
-                color[2] = (ramp & 0xFF);
-                break;
-
-            case 3: /* red: off, green: ramp down: blue: on */
-                color[0] = 0x00;
-                color[1] = 0xFF - (ramp & 0xFF);
-                color[2] = 0xFF;
-                break;
-
-            case 4: /* red: ramp up, green: off, blue: on */
-                color[0] = (ramp & 0xFF);
-                color[1] = 0x00;
-                color[2] = 0xFF;
-                break;
-
-            case 5: /* red: on, green: off, blue: ramp down */
-                color[0] = 0xFF;
-                color[1] = 0x00;
-                color[2] = 0xFF - (ramp & 0xFF);
-                break;
-        }
+#if 1
+        uint8_t color[3] = { 0, 0, 0 };
+        ramp = color_ramp(ramp +1, color);
 
         uint8_t i, j;
         for (i = 0; i < 16; i++) {