= 4) r += 0.05; // give bonus for gliding with no force

        // evolve state in time
        var ns = this.getState();
        var out = {'ns':ns, 'r':r};
        return out;
      }
    }
    
    function gofast() { steps_per_tick = 100; }
    function gonormal() { steps_per_tick = 10; }
    function goslow() { steps_per_tick = 1; }

    // flot stuff
    var nflot = 1000;
    function initFlot() {
      var container = $("#flotreward");
      var res = getFlotRewards();
      series = [{
        data