Version emulation
From Worms Knowledge Base
Since Deadcode (later joined by CyberShadow) started maintaining Worms Armageddon, many updates have been released and version emulation has rapidly been implemented in order to let players with different game logic versions play each other.
Picking the emulated version
In an online game with a mixture of players using different versions, the oldest version is the one emulated. So if someone joining a game using v3.6.31.0, and one of the players uses v3.6.29.0 and all other players use v3.7.2.1, then v3.6.29.0 would be emulated, because it is the highest version everyone would be able to emulate.
But there are some exceptions to that: if a host detects that some players in the game would improperly emulate the version that should be emulated (according to logic described above), then an older version is emulated. For example, v3.6.20.2 has an improper v3.6.20.1 emulation, and this case is handled in v3.6.20.3+. Thus, if, in a game hosted with v3.6.20.3+, there is a mixture of v3.6.20.1 and v3.6.20.2 players (and no older version is used), then the host would force emulating v3.6.19.19 rather than v3.6.20.1, in order to prevent v3.6.20.2 players from desynchronizing.
Similarly, there is backwards compatibility but not forwards compatibility when reading replay files. Thus, for example, a v3.6.31.0 user can watch replays recorded by W:A v3.6.31.0 or prior, but not those recorded with versions later than v3.6.31.0.
