For a long time, most advancements in video game realism have been in visuals; adding detail and resolution to the environments simulated. A recent trend, however, is to increase the realism of objects, their physical properties, and how they move. Since simulating the complex interchange of balance and animation required to actually pick up an object is beyond the flexibility of most present game engines, many games that allow object manipulation employ some form of invisible force: a tractor beam or telekinesis are the most popular choices. Examples of Ragdoll Physics include: