FUNDAMENTALS OF GAME DESIGN, SECOND EDITION

Real-Time Games Versus Turn-Based Games

Your specification of the core mechanics will read somewhat differently depending on whether your game is turn-based or takes place in real time.

Most video games operate in real time, so the core mechanics specify the parame­ters of a living world that operates on its own whether the player acts or not. Many of the mechanics you design will be processes that operate continuously or for extended periods. Al-driven characters go about their business, traps check to see
if they should spring upon anyone, banks collect and pay interest, and so on.

When you specify one-shot events rather than continuous processes, the events will often occur as a direct or indirect consequence of player actions or because some process detects a special condition, such as when a runner crosses the finish line in a race. (The later section "Mechanics" discusses events and processes in greater detail.)

In a turn-based game with no artificial opponents, the core mechanics don't do anything at all until a player takes his turn. Once he has done so, the core mechan­ics can compute the effects of his actions on the game world. Then the mechanics remain idle while the next player takes her turn, and so on. In some games, all the players enter their intended actions simultaneously while the mechanics remain idle; once the players finish for that turn, the core mechanics compute the effect of all players' actions.

In a turn-based game, then, your design for the mechanics will read like a specifica­tion for a sequence of events rather than a set of processes that operate all the time. You will state the effects of each possible action and what other computations take place as a consequence. Although you may design processes for a turn-based game, you must realize that processes do not really operate continuously; they only run between player turns. Your design for a process in a turn-based game must include points at which the process may safely be interrupted for the next player's turn.

In a turn-based game that does have artificial opponents or NPCs, the mechanics don't remain entirely idle between turns because they must compute the behavior of these characters. However, the artificial characters still act in turns, just as the player does.