old_contents: (function(World, View){
      var world = new World();
  
      var problem = world.createInvertedPendulum({ angle: Math.PI/50 });
  
      new View(document.getElementById('playground'), problem);
  
      function run(){
  	problem.tick();
  	requestAnimationFrame(run);
      };
      run();
  })(World, InvertedPendulumView);
  
new_contents: (function(World, View){
      var world = new World({ g: 1/16, M: 1/4 });
  
      var problem = world.createInvertedPendulum({ angle: Math.PI/50 });
  
      new View(document.getElementById('playground'), problem);
  
      function run(){
  	problem.tick();
  	requestAnimationFrame(run);
      };
      run();
  })(World, InvertedPendulumView);
  
subject: tweak world parameters for a fluent fall