The game is defined in a single file cloak.acl, which then merges in the library definitions.

#!../bin/jacl
#------------------------------------------------------------------------------
#                                                             CLOAK OF DARKNESS

constant game_title     "Cloak of Darkness"
constant game_author    "Stuart Allen"
constant game_version   1

integer blundered_in    1

{+intro
clear
write "^^"
style bold
write game_title
style normal
write " ported by " game_author ^^
print:
   Hurrying through the rainswept July night, you're glad to see the
   bright lights of the Opera House. It's surprising that there aren't more
   people about but, hey, what do you expect from a quick port of a cheap
   demo game...?^^
.
execute "+look_around"
}

location foyer : foyer
 short      the "foyer of the Opera House"
 north      outside
 south      bar
 west       cloak_room

{look
print:
   You are standing in a spacious hall, spendidly decorated in red
   and gold, with glittering chandeliers overhead. The entrance from
   the street is to the north, and there are doorways south and west.^
.
}

{movement
if destination = outside
   print:
      You've only just arrived, and besides, the weather outside seems
      to be getting worse.^
   .
   return
endif
return false
}

location outside : street outside
 short      the "street outside"

location cloak_room : small cloak room storage closet
 short      the "cloak room"
 east       foyer

{look
print:
   The walls of this small room were clearly once lined with hooks,
   though now only one remains. The exit is a door to the east.^
.
}

object hook : small brass hook peg
 short      a "small brass hook"
 has        SURFACE
 capacity   25

{examine
write "It's just a small brass hook, "
if cloak(parent) = hook
   write "with a cloak hanging on it.^"
else
   write "screwed to the wall.^"
endif
}

location bar : bar
 short      the "foyer bar"
 has        DARK
 north      foyer

{look
print:
   The bar, much rougher that you'd have guessed after the opulence of
   the foyer to the north, is completely empty. There seems to be some
   sort of message scrawled in the sawdust on the floor.^
.
}

{movement
if here has DARKNESS
   if destination != foyer
      write "Blundering around in the dark isn't a good idea!^"
      set bar(blundered_in) + 1
      return
   endif
endif
return false
}

object message : message sawdust floor
 short      a "scrawled message"

{read : examine
if bar(blundered_in) < 2
   print:
      The message, neatly marking in the sawdust, reads...^^
      ~You have won!~^
   .
   points 50
   execute "+game_over"
else
   print:
      The message has been carelessly trampled, making it difficult
      to read. You can just distinguish the words...^^
      ~You have lost.~^
   .
   execute "+game_over"
endif
}

{+eachturn
if here hasnt OUTDOORS
   move north_wall to here
   move south_wall to here
   move east_wall to here
   move west_wall to here
endall
}

object kryten: myself self me
 has        ANIMATE
 short      name "yourself"
 quantity   42
 parent     foyer
 player

{examine_override
execute "+inventory"
}

object cloak : dark black velvet cloak
 short      a "velvet cloak"
 long       "Lying on the ground is a handsome velvet coat."
 has        WEARABLE WORN
 parent     kryten
 mass       5

{examine_override
print:
   A handsome cloak, velvet trimmed with satin, and slightly spattered
   with raindrops. Its blackness is so deep that it alsmost seems to suck
   light from the room.^
.
}

{drop
if here != cloak_room
   write "This isn't the best place to leave a smart cloak lying around.^"
else
   proxy "hang cloak on hook"
endif
}

{insert_on_hook_override
write "You hang the cloak on the hook.^"
move cloak to hook
ensure bar hasnt DARK
if hook hasnt SCORED
   points 50
   ensure hook has SCORED
endif
}

{take_override
write "You take the cloak back off the hook.^"
move cloak to player
ensure bar has DARK
}

grammar hang *held on *present  >insert_on

{+dark_description
write "You are in complete darkness.^"
}

{+no_light
print:
   It's very dark in here. Perhaps you should just leave before you
   do any damage.^
.
set bar(blundered_in) + 1
set time = false
}

{+title
if player has SITTING
   write "(sitting)^"
endif
}

object north_wall: north north wall
 has            NO_TAB
 short          the "north wall"

object south_wall: south southern wall
 has            NO_TAB
 short          the "south wall"

object east_wall: east eastern wall
 has            NO_TAB
 short          the "east wall"

object west_wall: west western wall
 has            NO_TAB
 short          the "west wall"

object ground: ground floor
 has            SURFACE NO_TAB
 short          the "ground"

#include "verbs.library"