Game Dynanics
The game dynamics both defines and delimits play.
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Dynamics, typically in the form of context trajectories, is the heart and soul of all games, real or imagined. Every legal (game-defined and game defining) action is fixed by its dynamics, what the game allows to happen and what it doesn't allow -- all agreed to as convention in advance by the participating members of the game.
For example, in my own games, Select 'n Shoot, which, as the name implies, are target-shooting games (where the gun is a tennis racket, the bullet is a ball, and the target is some spot on the other side of the net), ball trajectory is central.
On the planet Ceerkus, as another example, when Prince Arlin scales the formic rock and fires his carbonide missile at the foundation of the evil ruler's fortress, the climb, the weapon, and the resulting explosion have to satisfy the gravitational and inertial forces on the planet. The overall trajectory is well-defined. Arbitrariness isn't an option.
It's the same for Jeremy Bentley when he slams the tennis ball back over the net to the reigning champion of the circuit. The ball can't just fly off to heaven and return in a roundabout way to the champ -- it must move in accordance with recognized court dynamics.
And it holds true for the champ, who races to intercept the return. Topflight performance presumes excellent conditioning and acceleration, as well as natural speed. It also assumes a court surface with the appropriate friction between surface and shoes to accommodate the motion. And it depends on how far from the ball the champ happens to be, how fast the ball is moving, and how quickly he or she can move to reach it. These factors are all part of the complex physical, psychological, and physiological dynamics of the context.
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Considering the dynamics of tennis in more detail, you can add a level of capability of the athlete to read the ball trajectory. Perceptual skill at some level is required to be able to estimate the pace of the ball and tell from the measured speed where it is possible to make an intercept, for any given shot from the opponent. You would also have to know what kind of shot you might use at the intercept location if and when you get there. The two critical facets of the game -- intercept and hitting -- go together intimately and call for precisely defined dynamics. Not easy to formulate, but necessary. Rules are needed.
On a lob, for instance, you certainly don't pick a low point of the path to try to hit an overhead smash. Nor is it sensible to go for an under spin drive at the top of a flat but shoulder high trajectory - you need a downward racket motion to get effective under spin. On the other hand, when the ball is on its downward arc, a topspin shot can be very effective, just as a high point on an upward arc can be a good spot for a hard flat drive. You need to know your trajectories to make good decisions here.
