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I spent the last two years coding a reimplementation of A Game of Thrones: The Board Game[1], and I would use this paradigm if I had to recode it. Sharing the code between the client and the server brings a lot to the table. Having to wait for the server for the set of legal moves feels like a hack. It's way simpler to have the client have its own copy of the game state, and allow "query" methods (methods that fetches data about the game state but don't modify it). This allows you to make _powerful_ UI, which can show any kind of information the user needs about the game like predictions about what would happen if a move is done, computing things so the user doesn't need to. If I had to redo it, I would use a paradigm similar to how boardgame.io[2] works, which is similar to how fixed lockstep works. The server and the clients all keep a full state of the game and when a player makes an action, it is transmitted to all the actors, who apply this action to their own state of the game. Since the game rules are deterministic, the final state of the game will be the same for each actor. The only 2 complex to handle are randomness and secrets (the former can actually be solved by the later), but overally, the complexity is managed elegantly and you can separate networking code from gameplay code easily. Actually, one of my future possible project would be to make a library similar to boardgame.io, but less opiniated, and in the future, offer a platform to easily host and launch a game coded with it. [1] https://boardgame.io/ [2] https://swordsandravens.net/ |
But you are waiting for the server anyway - that's the "turn" in "turn-based". The way I build, the notification about your turn simply comes with the moves you can make as well - and the moves you can make don't change, because _it's your turn_, so there's no limit to how powerful a UI you can make with it.
Take chess for example (it was while implementing chess that I worked out this paradigm, actually) - a move from the server (sent in a packed binary format) was a mapping of start and end positions and a metadata byte that linked it to a kill, a promotion, or castling. and it was rare indeed that a complete payload (with a full set of currently legal moves + effects) would be up to two kilobytes. The client would deserialise that and of course could show you possible moves when you selected a piece and so on.
> The server and the clients all keep a full state of the game and when a player makes an action, it is transmitted to all the actors, who apply this action to their own state of the game.
This is actually what my current approach was born out of! But then I wanted to build a second client app, and I felt it was a pain to rewrite the game logic in another language - one solution to that is to have an isomorphic application, but in my case I decided to try out moving as much as possible to the server and just focusing on data parsing and rendering on the client and it worked out surprisingly well. It also let me do things like implement custom rulesets with much greater ease, because the rule logic exists solely on the server and you can deploy/modify that without requiring the clients to update.