Prototype Hydra chess game on testnets

[abailly-iohk]

Why

• We want to "eat our own dog food", eg. use the technology we are building on a daily basis in order to:
  • Test our own stuff
  • Improve the overall user experience, even though developers can tolerate more complex UIs than the average user
  • Experience running an app/system
• Games where plays are run in a Hydra head with only results/leaderboards being kept on L1 seem a good use case for Hydra Head protocol
• Chess being a well-known deterministic game, with simple rules, few players, easy to build interface, is a good candidate
• Yet it's also challenging to provide a great UX so that it's fast and easy to setup a game
• We want to improve the DX for people wanting to build stuff on top of Hydra, this app will be a "reference DApp", something we can point people at and refer to when improving Hydra

What

• The application should be easy to install even for users unfamiliar with cardano-node and hydra-node

  • Having a short and sweet README.md on a dedicated repository (e.g. hydra-chess) could be a good goal post here.
  • Users can build the hydra-chess on their machines or download pre-built binaries when/if available

• Two users can play a Chess game using Cardano on any public testnet

  • They run the hydra-chess application locally selecting which public network to run on which provides some command-line interface
  • Users are guided to through the full life-cycle of the game

• The user journey of the this guided chess experience covers:

  • exchange connectivity information provided by the interface and use that to configure known peers
  • initialise a new head
  • start a new game once the head is opened
  • play game using some simple interface and board display
  • see the result of the game
  • start and play one or more other games in the head
  • close the head once they don't want to play anymore
  • have the game(s) results be reflected on L1

• The UI provided is terminal user interface (TUI) with no specific need for scriptability

• Out of scope: Fancy graphical user interfaces or an exposed API

• Out of scope: Security is not the main concern at this stage, so non-validating scripts (about game logic or elo rating) are acceptable

Non-functional requirements:

• OS support limited to Linux/Mac OS
• Users should have a good knowledge on their machine and network configuration (eg. be able to tweak firewall to let other people connect to their node)

How

• Provide a wrapping application managing all the tools needed: Hydra node, cardano-node, perhaps even a small wallet
  • Configuration and data is handled through XDG directories
  • This could be further improved by packaging the whole set of needed binaries in a single native package to offer users a native installer experience ➡️ Simple installation packages for Hydra node #1107
• Player can start playing by minting a token on L1 and consuming it for starting a game
  • There's a dedicated minting policy which is used to mint a token for some specific pubkeyhash, and is packed with a UTxO holding some ADAs to be able to pay for collateral inside the head
  • Inside the Head, the token is locked to a script named elo-script with intention this will control changes in ELO ratings following conclusion of a game
• Provide a way to configure peers
• Write a smart contract ensuring all moves are legal
• Separate more cleanly UI code from backend code and expose a proper API
• Provide a command-line user interface covering the complete life-cycle of one or more games with another player
• Code is available under cardano-scaling organisation with enough instructions to get started

[abailly-iohk]

@rezabaram and I were able to play a game to completion, running on our own machines 🎉

[ch1bo]

A dedicated repository has been set up and equipped with instructions in a README.md: https://github.com/cardano-scaling/hydra-chess/tree/eb786daf5204e1c807fde10cdbbe237041fa439c

[ch1bo]

@abailly-iohk Reviewed instructions and overall look fine, only suggestion: cardano-scaling/hydra-chess#1