DEF turn Script {
   url "javascript:
        function set_fraction(frac, eventTime) {
           if (running == true) {
              if (frac < oldFrac) {
                 tick = tick + 1;
                 if (tick > 299) tick = 0;
                 value_changed[3] = -tick * 2.0 * 3.14159/300.0;
                 value_changed[0] = 0.0;
                 value_changed[1] = 0.0;
                 value_changed[2] = 1.0;
              }
              oldFrac = frac;
           }
        } 

        function stop_start(bval, eventTime) {
           if (bval == true)
              running = !running;
        }

        function reset(bval, eventTime) {
           if (bval == true) {
              tick = 0;
              value_changed[3] = 0.0;
           }
        }"