text: var LifelikeWorld = (function () {
  
      function LifelikeWorld(map, legend) {
          World.call(this, map, legend);
      }
      LifelikeWorld.prototype = Object.create(World.prototype);
  
      var actionTypes = Object.create(null);
  
      LifelikeWorld.prototype.letAct = function(critter, vector) {
          var action = critter.act(new View(this, vector));
          var handled = action &&
              action.type in actionTypes &&
              actionTypes[action.type].call(this, critter,
                  vector, action);
          if (!handled) {
              critter.energy -= -0.2;
              if (critter.energy <= 0)
                  this.grid.set(vector, null);
          }
      };
  
      return LifelikeWorld;
  
  })();