Jet Set Willy Terminology
                 As Explained by Andrew Broad
       As posted to the JSW&MM Mailing List, 03-Apr-2004

Each room in JSW can have up to eight guardians (horizontal,
vertical, arrows or ropes). I call these "guardian-instances"
because each one is an instance of a "guardian-class".

A regular JSW game can have up to 127 guardian-classes, which are
stored in a table separate from the rooms.

Each guardian-instance specifies the start-column (if it's a
horizontal guardian), column (if it's a vertical guardian or a rope)
or row (if it's an arrow), and also specifies the start-sprite
(within the sprite-page, which is specified in the guardian-class).

Each guardian-instance specifies which guardian-class it is an
instance of, and all the other data are specified in the guardian-
class.

Guardian-class data include which type of guardian it is (HG, VG,
rope or arrow), its colour-attribute, its row (if it's a HG), start-
row (if it's a VG), start-column (if it's an arrow), path-
boundaries, sprite-page and animation-mask.

A sprite-page is a 256-byte area of memory which stores the graphics
for guardian-classes which use that sprite-page. Any 256-byte area
whose start-address is divisible by 256 can be used as a sprite-
page, although many such areas are unsafe to edit because they are
used for other things (i.e. they can be read as sprite-pages, but
must not be overwritten).

[snip]

--
Dr. Andrew Broad
http://abroad.sqweebs.com/
http://abroad.sqweebs.com/spectrum/
http://abroad.sqweebs.com/spectrum/mmjsw