====== Frame skipping ======

Once in a while you created some effect that just goes too quick when you update it every frame.
The option is to have a check in order to skip your routine every other frame.
Put this inside your IRQ.

<code>
start:
   inc skipper+1      // increase the check byte
   
skipper:
   lda #$00           // check byte
   and #$01           // check first bit (even or odd number?)
   beq passroutine    // skip routine on even numbers
   
routine:
   // routine that will be executed every other frame
   
passroutine:
   // the rest, executed every frame</code>