A waterskin that is depleted as the player drinks from it.

"Thirst"
The player carries a waterskin. The waterskin can be full, partly drained, or empty. The waterskin is full. Understand "water" as the waterskin.
Instead of drinking the waterskin when the waterskin is empty:
   say "There is no water left."
Instead of drinking the waterskin: if the waterskin is partly drained, now the waterskin is empty; if the waterskin is full, now the waterskin is partly drained; say "You drink a long draught."
After printing the name of the waterskin: say " ([waterskin condition])"
Campsite is a room. "It is solid night now, and the stars have come out. Unfamiliar stars. On the other side of the valley -- a valley round-bottomed but shallow, like a soup bowl -- burn other campfires, most likely bandits. Their voices do not carry, but the smoke rises and obscures the starlight over that way."
A sleepsack is an enterable container in the Campsite. "Your sleepsack is laid out in a pocket of sandy soil and coarse grass."
The sandy soil, the stars, the distant campfires, and the coarse grass are scenery in the Campsite. Understand "smoke" as the campfires. Instead of listening in the presence of your campfire: say "All you hear are the reassuring snaps and cracks of the sticks in your fire." Understand "campfires" or "fires" as the distant campfires.
Your campfire is scenery in the Campsite. Instead of pushing, pulling, turning, tasting, or touching your campfire, say "You would burn yourself." Understand "fire" as your campfire. The description of your campfire is "A reassuring protection against wild animals and cold."
The description of the stars is "You invent constellations for them. The slingshot. The scroll. The heart (upside down)."
Instead of going nowhere when the player is in Campsite:
   say "Now is not the time for wandering, alone in the dark. Better to keep here[if your campfire is visible], by the fire[end if]."
Singing is an action applying to nothing. Understand "sing" as singing.
Instead of singing:
   say "You sing, deep and low, a song from home. It is a good night for singing and the song raises your spirits."
Test me with "i / drink water / i / drink water / i".
Test me with "i / drink water / i / drink water / i".
Campsite
It is solid night now, and the stars have come out. Unfamiliar stars. On the other side of the valley -- a valley round-bottomed but shallow, like a soup bowl -- burn other campfires, most likely bandits. Their voices do not carry, but the smoke rises and obscures the starlight over that way.

Your sleepsack is laid out in a pocket of sandy soil and coarse grass.

>(Testing.)

>[1] i
You are carrying:
a waterskin (full)

>[2] drink water
You drink a long draught.

>[3] i
You are carrying:
a waterskin (partly drained)

>[4] drink water
You drink a long draught.

>[5] i
You are carrying:
a waterskin (empty)