diff --git a/source.asm b/source.asm
index 5d3b65a..0ffc7ed 100644
--- a/source.asm
+++ b/source.asm
@@ -220,35 +220,71 @@ mainloop:
   ; debug command, use w 0 100 2 to set a breakpoint here
   clr.w $100
 
+  move.w #0,d2
+  move.w #0,d3
   ; detect joystick left/right
-  move.w #0,d1
-  ; move.l #%100000010,d2
-  ; and.l JOY1DAT,d2
-  move.w JOY1DAT,d2
-  btst.l #9,d2
+  ; move.w JOY1DAT,d2
+  ; btst.l #9,d2
+  ; bne move_left
+  ; btst.l #1,d2
+  ; bne move_right
+  ; bra done_joy
+  ; jmp done_joy_left_right
+
+  ; http://eab.abime.net/showthread.php?t=75779&page=3
+  move.l JOY0DAT,d0
+  move.l d0,d1
+  add.l d1,d1
+  eor.l d0,d1
+  btst.l #9,d0  ; left
   bne move_left
-  btst.l #1,d2
+  btst.l #1,d0  ; right
   bne move_right
-  ; bra done_joy
-  jmp done_joy
+  bra joy_up_down
   move_left:
-    move.w #-1,d1
-    bra done_joy
+    move.w #-1,d2
+    bra joy_up_down
   move_right:
-    move.w #1,d1
+    move.w #1,d2
+  joy_up_down:
+
+  btst.l #9,d1  ; up
+  bne move_up
+  btst.l #1,d1  ; down
+  bne move_down
+  bra done_joy
+  move_up:
+    bra done_joy
+  move_down:
+    move.w #$100,d3
   done_joy:
+    move.w #-$100,d3
 
+  ship_update:
   ; animate the sprite
   ; first load the current x position (from ship address) into a data register
   move.w SHIP_DST,d0
-  ; add 1
-  add.w d1,d0
+  add.w d2,d0
   andi.w #$00ff,d0
-  ; AND with 0xff00?
   ; then write it back to the the ship address - it is the first word
-  and.w #$ff00,SHIP_DST
+  and.w #$ff00,SHIP_DST ; first zero the bits to be used for the new position
   or.w d0,SHIP_DST
 
+  bra skip
+  ; move vertically
+  move.w SHIP_DST,d0
+  add.l d3,d0
+  andi.l #$ff00,d0
+  and.l #$00ff,SHIP_DST
+  or.l d0,SHIP_DST
+
+  move.w SHIP_DST+1,d0
+  add.l d3,d0
+  andi.l #$ff00,d0
+  and.l #$00ff,SHIP_DST+1
+  or.l d0,SHIP_DST+1
+  skip:
+
   ; if mousebutton/joystick 1 or 2 pressed then exit
   ; mouse/joy button 1
   btst.b #6,CIAAPRA