Mine

alias Reaction { 
  if (!$window(@Reaction)) window -pfdok0w0o @Reaction 1 1 250 150 
  .timerreact -m 1 100 RReaction 
} 
alias RReaction { 
  Reactset 
  if ($1 != Norand) var %r = $r(1,20) 
  if (%r = 1) { 
    drawdot @Reaction 4 25 75 75 
    set %react.click $ticks 
  } 
  if (%r != 1) .timerreact -m 1 100 RReaction 
} 
alias Reactset { 
  drawfill @Reaction 1 2 1 1 
  drawdot @Reaction 0 25 75 75 
} 
menu @Reaction { 
  sclick: Reactclick 
} 
alias Reactclick { 
  if (%react.click) { 
    drawtext @Reaction 4 Arial 10 150 30 Reaction time of: 
    drawtext @Reaction 4 Arial 10 150 50 $calc(($ticks - %react.click) / 1000) secsonds. 
    drawtext @Reaction 4 Arial 10 120 100 Press space to restart. 
    drawdot @Reaction 3 25 75 75 
    unset %react.click 
  } 
  else { 
    drawtext @Reaction 4 Arial 10 150 30 Failed reaction. 
    drawtext @Reaction 4 Arial 10 120 100 Press space to restart. 
    .timerreact off 
  } 
} 
on *:keydown:@Reaction:32:RReaction 
on *:close:@Reaction: { 
  unset %react.* 
  .timerreact off 
}