GME Script line

A script line consists of a list of conditionals, a list of actions, and a so called playlist consisting media file table indices.

A script line has the format aaaa conditionals... bbbb actions... cccc media... where

• a is the number of conditionals. Each conditional consists of 8 bytes.
• b is the number of actions. Each action is 7 bytes.
• c is a playlist

Conditionals

The conditionals are of the format t1 aaaa cccc t2 bbbb

• t1 & t2 (uint8) type of a and b resp. (0 == register, 1 == value)
• a & b (uint16) value or id of register
• c (uint16) is the comparison operator The rest of the line is only considered when the comparison between the register and the value or other register holds.

Comparison operators

Known comparison operators are:

• FFF9 (written $r==m? in tttool's output and the yaml files): Equality
• FFFA (written $r>m? in tttool's output): Greather than
• FFFB (written $r<m? in tttool's output): Less than
• FFFD (written $r>=m? in tttool's output): Greater or equal
• FFFE (written $r<=? in tttool's output): Less or equal
• FFFF (written $r!=m? in tttool's output): Not equal

Actions

The actions are of the format rrrr cccc tt mmmm

• r (uint16) id of register
• c (uint16) is the command
• t (uint8) type of m (0 == register, 1 == value)
• m (uint16) value or id of register

Commands

Known commands are:

• FFF0 (written $r+=m): Increment register $r by m or value of $m
• FFF1 (written $r-=m): Decrement register $r by m or value of $m
• FFF2 (written $r*=m): Multiply register $r by m or value of $m
• FFF3 (written $r%=m): Set register $r to $r mod m
• FFF4 (written $r/=m): Set register $r to $r div m
• FFF5 (written $r&=m): Bitwise add to register $r the value of m
• FFF6 (written $r|=m): Bitwise or to register $r the value of m
• FFF7 (written $r^=m): Bitwise xor to register $r the value of m
• FFF8 (written Neg($r)): Negate register $r.
• FFF9 (written $r:=m): Set register $r to m or value of $m
• FFE0 (written P(): play one random sample of the media list
• FFE1 (written P(): play all samples of the media list
• FFE8 (written P(m)): Play audio referenced by the mth entry in the indices list.
• FB00 (written P(b-a)): Play all samples from that inclusive range. a := lowbyte(m), b := highbyte(m)
• FC00 (written P(b-a)): Play one random sample from that inclusive range. a := lowbyte(m), b := highbyte(m)
• FD00 (written G(m)): Begin game m.
• F8FF (written J(m)): Jump to script m.
• FAFF (written C): Cancel game mode.

Currently unknown commands are FE00 and FF00 (in theory there can be more but these have been seen in the wild, at least).

The commands P, G , J and C seem to ignore their registers, C also its parameter (which always is FFFF).