function controlFunction(block)
  {
  const max_force=1000000000;
  const margin=0.01;
  const friction_comp=0.2;

  if(block.x<-1-(margin/2))
   return max_force*(1+friction_comp);
  else if(block.x<-1.15*margin)
   return -max_force;
  else
   return -block.x;
}