code: @Override
      public void die(String reason) {
  	log.info("[die] Robot {} died with reason: {}", serialNumber, reason);
  	if (alive) { // if not alive it means it was killed at creation
  	    alive = false;
  	    interrupted = true; // to speed up death
  	    world.remove(Robot.this);
  	}
  
      }
docs: Kills the robot and removes it from the board
  
  @param reason user-friendly explanation for the death