Suppose our game features a detailed simulated combat between the player character and his opponent. He might have several weapons available, and several types of attack available; and at any given time he might be perched up in the rigging of his ship, standing on the open deck, or boxed in between some barrels. His options will vary depending on his position, and obviously it would detract from the pacing to make the player keep LOOKing in the middle of combat in order to remind himself where he is. Instead, we'll roll this information into the command prompt:

"Don Pedro's Revenge"

The Deck of the Helene Marie is a room. "The two crews are embattled all around you, but your attention is reserved for your particular enemy: Don Pedro."

Table of Random Prompts

position	prompt
boxed	"So securely boxed-in that you can really only parry or thrust, you try to "
boxed	"Trapped between your barrels, you decide to "
perched	"Able to slice at your attackers but not to advance or retreat, you choose to "
perched	"Perched up here with the advantage of height (but little mobility), you attempt to "
free	"Out on the open deck with no impediments, free to advance or retreat, you decide to "

When play begins: reset the prompt.

Every turn: reset the prompt.

To reset the prompt:
    sort the Table of Random Prompts in random order;
    repeat through the Table of Random Prompts:
        if the position entry is the placement of the player:
            now the command prompt is prompt entry;
            stop.

After reading a command: say conditional paragraph break.

A placement is a kind of value. The placements are boxed, perched, free. The player has a placement. The player is free.

Understand "retreat" or "parry" as retreating. Retreating is an action applying to nothing.

Check retreating:
    if the player is perched, say "You can't move backward or parry very successfully from this position." instead.

Carry out retreating:
    now the player is boxed;
    say "You protect yourself, but end up wedged in between two barrels."

Understand "thrust" or "advance" as advancing. Advancing is an action applying to nothing.

Check advancing:
    if the player is perched, say "You can't move forward from here, only slash." instead.

Carry out advancing:
    now the player is free;
    say "You push forward aggressively, making your way to the open deck."

Instead of jumping:
    now the player is perched;
    say "You leap and swing yourself boldly up into the rigging, leaving your attackers beneath you."

Instead of jumping when the player is perched:
    now the player is free;
    say "You leap down from your position, into the middle of the deck."

Test me with "advance / jump / advance / retreat / jump / retreat / retreat / advance".

Of course, this won't be much fun until we also provide the player with a few weapons, some more fighting maneuvers, and, most of all, a Don Pedro to defeat.