Upgrading and other engines

From 1.x to 2.x

Version 2 changed territory keys, indices, names and counts to the classic world/Europe boards. Compact kept version 2 and JSON format 2 refuse version 1 games instead of replaying their indices on another map. Preserve old software alongside old records if you must inspect them; begin new 2.x games explicitly. Oceania became australia in continent keys. The 2.0 changelog preserves the full changes.

Updating within 2.x

2.1 added optional card/dice dressing; plain and dressed tables run the same rules. Preserve seeds, map and move records. A seed alone is not enough without table settings and compatible rules.

Coming from mutable or network engines

Use a new returned game for each legal transition, and treat null as refusal. Keep names local and separate presentation from rules. A host can transport moves, but should replay and validate them instead of trusting client boards. Keep external coordinates and card indices mapped to the selected native board. State design and save/restore explain the integration.