Free Hero Mesh

  created, destroyed, or moved. It still receives broadcast messages
  normally, and can also be addressed specifically.

(CollisionLayers <userflags...>)
  Define user flags as CollisionLayers bits; the first defined flag is
  bit0. Up to 8 flags can be defined in this way.

(LevelTable <definitions...>)
  Define the level table. See the section about level table definition
  for details. Can only occur once.

(Misc4 <userflags...>)
  Define user flags as Misc4 bits; the first defined flag is bit0. Up to
  32 flags can be defined in this way.

(Misc5 <userflags...>)
  Define user flags as Misc5 bits; the first defined flag is bit0. Up to
  32 flags can be defined in this way.

* The way that the trigger phase works is different.

* In the ARRIVED and DEPARTED messages, Arg1 is always zero.

* Diagonal shoving is not possible.


=== Level table definition ===

The following blocks are allowed in a level table definition:

(<label> <code...>)
  Define a data column. The SQL name of the data column will be that of
  the label name, preceded by a underscore, and some characters will be
  stripped out.

(<string> <label> <width> <format> <color>)
  Defines a display column. The <label> is the name of the data column.
  The <width> is a number 1 to 255 or it can be * for fill width. The
  <format> is a string of one or two characters; see the below list of
  possible formats. The <color> is the text colour, and is optional; it
  can be a number from 1 to 255, or it can be a sequence of parenthesized
  pairs of a number (-127 to +127) and colour, to mean use those colour if
  the value of this column is in range. It uses the colour for all values
  up to and including the specified number, so the numbers should be listed
  in ascending order, in order to work. The <string> is the heading; it is
  not allowed to include control characters, nor can it include graphic
  characters with code number less than 32.

(<local> <type> <code...>)
  Defines a aggregate calculation. The <local> is the name of the aggregate
  to be referred by other blocks. The <type> is the type of aggregate,
  which can be one of: + for the sum, min for the least value (unsigned),
  max for the greatest value (unsigned), ,min for the least value (signed),
  and ,max for the greatest value (signed).

(TODO: Mention valid instructions.)