diff --git a/compiler/res/prog8lib/c64utils.p8 b/compiler/res/prog8lib/c64utils.p8
index 8a801b628..432a2da31 100644
--- a/compiler/res/prog8lib/c64utils.p8
+++ b/compiler/res/prog8lib/c64utils.p8
@@ -593,6 +593,9 @@ asmsub  scroll_left_full  (ubyte alsocolors @ Pc) clobbers(A, Y)  {
 	; ---- scroll the whole screen 1 character to the left
 	;      contents of the rightmost column are unchanged, you should clear/refill this yourself
 	;      Carry flag determines if screen color data must be scrolled too
+
+	; TODO why are the two inner loops split apart? can't they just be one single .for/.next macro?
+
 	%asm {{
 		stx  c64.SCRATCH_ZPREGX
 		bcs  +
diff --git a/examples/skramble.p8 b/examples/skramble.p8
index c10557045..fb4a5ce9c 100644
--- a/examples/skramble.p8
+++ b/examples/skramble.p8
@@ -7,10 +7,16 @@
 
 main {
 
+    ubyte perform_scroll = false
+
     sub start() {
         c64scr.plot(30,2)
         c64scr.print("skramble !")
 
+        c64.SCROLX = c64.SCROLX & %11110111     ; 38 column mode
+
+        c64utils.set_rasterirq(1)     ; enable animation
+
         ubyte target_height = 10
         ubyte active_height = 25
 
@@ -20,17 +26,21 @@ main {
             } else if active_height > target_height {
                 active_height--
             } else {
-                target_height = 10 + rnd() % 13
+                target_height = 8 + rnd() % 16
                 continue
             }
 
+            while not perform_scroll {
+                ; let the raster irq do its timing job
+            }
+            perform_scroll = false
             c64scr.scroll_left_full(true)
             ubyte yy
             for yy in 0 to active_height-1 {
-                c64scr.setcc(39, yy, 32, 2)
+                c64scr.setcc(39, yy, 32, 2)         ; clear top
             }
             for yy in active_height to 24 {
-                c64scr.setcc(39, yy, 102, 8)
+                c64scr.setcc(39, yy, 102, 8)        ; draw mountain
             }
 
             yy = rnd()
@@ -68,11 +78,16 @@ main {
 ;            c64scr.setcc(1, 10, @'=', 15)
 ;            c64scr.setcc(2, 10, @'>', 15)
 
-            for A in 0 to 4 {
-                while @($d012) != 100 {
-                    ; just wait for the raster beam...
-                }
-            }
         }
     }
 }
+
+
+irq {
+    ubyte smoothx=7
+    sub irq() {
+        smoothx = (smoothx-1) & 7
+        main.perform_scroll = smoothx==0
+        c64.SCROLX = (c64.SCROLX & %11111000) | smoothx
+    }
+}