Fix problem where sometimes the right cap of a floor is not correctly cleared as it scrolls off the screen. The problem is that we need to delay moving the grid along to the next floor until after the old base grid has been fully cleared.

colourgo/game.s

@@ -1004,6 +1004,7 @@ yPos:    .BYTE $00
     lda gridXPos
     cmp (LEVELADDR),y
     bcc @return
+    beq @return
 
 ; At this point, we know that this grid is not visible
 ; Check to see if the start of the next grid is left justified