Gases

Virtual worlds rarely implement gases, and when they do it’s often as consequent properties of a location or some other object, rather than as objects in their own right.

The reasons for this are to do with the physical properties of gases (and of gas-borne particles, such as pollen and smoke). Gases are everywhere, they have miscibility and divisibility issues even worse than those of liquids, and they’re hard to contain.

Characters can do simple things like breathe them and smell them, but anything much more sophisticated entails capturing the gases, which then renders them inaccessible without the right apparatus. Some virtual worlds have gases dropped by certain monsters on death, but the result is rather clunky.

Air (or atmosphere) can conveniently be regarded as a generator object that’s available to all locations and containers. Sometimes, though, it’s useful to represent chunks of gases with unusual properties as separate objects. This allows for gusts of winds, clouds of dust, explosions, temperature gradients, swarms of tiny insects, foul stenches, and so on.

On the whole, though, the only gas that virtual worlds really need to consider is air, and then only for completion. Graphical worlds don’t need even air ¹—it’s “what there is when there’s nothing else there”—but textual worlds should account for it because players in that context reference objects by name, rather than by pointing device.