18xx Game Engine

The 18xx series of board games is of great fascination to me.

However, the parts which are interesting are the human interaction; the actual physical actions (computing best paths, keeping tabs on other players and their cash) don't appeal to me.

This is a quiet experiment with implementing the rules as a daemon in Python. With some effort, I assume different front-ends will be able to hook into the Daemon, giving us much more flexibility when creating front ends for the game.

Configuration Modules

Each game variant under app/config/ exposes a configuration module. In addition to the lists of private and public companies, the modules now provide:

• TOKEN_COUNTS – mapping of public company IDs to their starting token supply. Each PublicCompany instance created from the module also has a token_count attribute populated from this mapping.
• TRACK_LAYING_COSTS – the cost in currency for laying track tiles by Color.
• SPECIAL_HEX_RULES – a dictionary mapping hex identifiers to rule dictionaries or messages. Rules can specify no_lay, no_upgrade or allowed_colors to fine tune what track placements are allowed.

Token Availability

Public companies now track how many station tokens they have left using a tokens_available counter. Each token can also have a different cost as defined in the company configuration. When a token is purchased during an operating round its cost is deducted from the company's cash and the available count is reduced. The total number of tokens a company begins with is stored in the token_count attribute. At the start of a game tokens_available will equal token_count. Purchasing station tokens decreases tokens_available but does not change token_count. Each company also tracks whether it has already placed a station token in the current operating round and the engine enforces the rule that at most one token may be placed per round.

Dividend Payouts

Operating round moves must explicitly state whether dividends will be paid with the pay_dividend flag. This value must be True or False and a company can only choose once it has calculated income by running routes. When creating an OperatingRoundMove the flag defaults to False so tests and simple integrations may omit it. When dividends are distributed that income is removed from the company and credited directly to the players according to their share percentage.

Changelog

• Recent updates include initial handling of bankrupt companies when trains rust. Public companies now track placed station tokens and expose a hasValidRoute helper used during operating rounds to determine whether a company can continue operating once its trains are gone. Token placement is now limited to one per operating round and the flag resets at the start of each round. Track placement now checks each variant's SPECIAL_HEX_RULES. Hex rules can forbid initial placement (no_lay), upgrades (no_upgrade) or limit allowed tile colours. Moves violating these restrictions are rejected.

• Routes are now checked against the capacity of the trains assigned to a company. Each list of stops must form a continuous path across existing track tiles and cannot exceed the length of any available train. Invalid routes are rejected during the operating round.

• The presidency of a public company transfers only to the largest shareholder who holds at least 20% of its stock.