Rideable Vehicles by Graham Nelson begins here.

"Vehicles which one sits on top of, rather than inside, such as elephants or
motorcycles."

A rideable animal is a kind of animal.
A rideable animal is always enterable.
A rideable animal is usually not portable.
A rideable animal is an Inform library supporter.
Include (- with before [; Go: return 1; ], -) when defining a rideable
animal.

A rideable vehicle is a kind of supporter.
A rideable vehicle is always enterable.
A rideable vehicle is usually not portable.
Include (- with before [; Go: return 1; ], -) when defining a rideable
vehicle.

Definition: Something is vehicular if it is a vehicle or it is a
rideable animal or it is a rideable vehicle.

Mounting is an action applying to one thing.

Before entering a rideable animal (called the steed), try mounting the
steed instead.

Before entering a rideable vehicle (called the conveyance), try mounting the
conveyance instead.

Before getting off a rideable animal (called the steed), try dismounting
instead.

Before getting off a rideable vehicle (called the conveyance), try
dismounting instead.

Check mounting:
	if the noun is not a rideable animal and the noun is not a rideable
	vehicle, say "[The noun] cannot be ridden." instead;
	abide by the determine common ancestor for entering rule;
	abide by the can't enter something carried rule;
	abide by the implicitly pass through other barriers rule.
	
Carry out mounting:
	consider the standard entering rule.

Report mounting:
	say "You mount [the noun].";
	consider the describe contents entered into rule.

Understand "ride [something]" as mounting.
Understand "mount [something]" as mounting.

Dismounting is an action applying to nothing.

Check dismounting:
	if the player is not carried by a rideable animal and the player is
	not on a rideable vehicle,
		say "You are not riding anything." instead.
	
Carry out dismounting:
	if the player is carried by a rideable animal (called the steed),
		change the noun to the steed;
	if the player is on a rideable vehicle (called the conveyance),
		change the noun to the conveyance;
	consider the standard exiting rule.

Report dismounting:
	say "You dismount [the noun].";
	consider the describe room emerged into rule.

Understand "dismount" as dismounting.

Before asking a rideable animal (called the mount) to try going a
direction (called the way):
	if the player is carried by the mount, try going the way instead.

Rideable Vehicles ends here.

---- DOCUMENTATION ----

Inform's built-in "vehicle" kind assumes that the vehicle is a
container, which is fine for cars or hot-air balloons, but not so
good for a pony or a four-wheeled lawnmower, which one rides rather
than gets inside. Rideable Vehicles is an extension which creates
two more kinds: "rideable animal" (good for the pony) and
"rideable vehicle" (good for the lawnmower).

	The pony is a rideable animal in the Forest Clearing.
	The lawnmover is a rideable vehicle in the Garden Shed.

This means that three different kinds of thing can be used as a
means of travel, which might make it awkward to write a general
rule about them, so we also define the adjective "vehicular" for
any thing of any of these kinds.

	The Transport Museum is a room. "The Museum is filled with means of transport old and new, including [list of vehicular things in the Transport Museum]."

A new action called "mounting" is created, and a new command "mount"
(or "ride") is added for the player to use. Thus:

	Instead of mounting the pony, say "The pony snorts and backs off."

results in

	>ride pony
	The pony snorts and backs off.

And a corresponding "dismounting" action handles the command "dismount".

	>dismount
	You get off the pony.

Moreover, commands such as "get off the pony" or "get on the lawnmower"
are converted into these new actions instead, so that rules like the
following will always work, no matter what command is tried:

	Instead of mounting the tricycle when the transport pass is not carried by the player:
		say "The tricycle can only be ridden by those with a transport pass."

Lastly, a special rule means that "pony, go east" is recognised when
the player is riding the pony. (This works for rideable animals, but not
rideable vehicles.)