private void SetSolarSystem(){
	String full_path = "force."+forceName;
	try {
		gravity = (Force) Class.forName(full_path).newInstance();
	}  catch (ClassNotFoundException e) {
		System.err.println("Can't get class "+full_path);
	}  catch (InstantiationException e) {
		System.err.println("Can't instantiate class "+full_path);
	}  catch (IllegalAccessException e) {
		System.err.println("Can't access class "+full_path);
	}  
	gravity.solar_system_scale=BOX_WIDTH/8;
	gravity.setOffset(forceOffset);

	top_loss=bot_loss=0;
	loop_counter=0;
	this.solarSystem = new SolarSystem(numberOfPlanets, 
								BOX_HEIGHT,
								BOX_WIDTH,
								gravity,
								centrifugal_flag,
								averageEnergy,
								sun_flag,
								sun_size,
								random_radii_flag,
								random_position_flag,
								random_colour_flag);
   }