gcl0x

zpReset=$36                     {Relocate variables because vIRQ uses $30..$35}

\vIRQ_v5 p=
[def                            {Interrupt handler}
  $901 p= peek 1+ p.            {Flash second pixel}
  226 \frameCount.              {256-30: next interrupt after .5 second}
  \vIRQ_Return 0??              {vRTI sequence}
] p:

$800 q=                         {Main loop}
[do 1+ q. loop]                 {Flash first pixel}