Potential Battleship Royal on Miden

[Dominik1999]

Potential Battleship Royal on Miden

I want to discuss a PoC for a novel type of blockchain game. Battleship, the classic game, is a nice showcase for blockchains using client-side proofs. Basically, users want to hide the position of their ships from their enemies, but we still need to know that every ship is placed in a valid position. On Miden, however, we can think of the massive multiplayer version of this.

What is Battleship Royal?

There are different players, and all have their own naval fleets. There is still a map on which we can put a grid that provides us with coordinates. Players place ships onto the coordinates and play battleships, basically trying to hit each other's ships. However,

• Ship movement:
  • Players can move their ships
  • Undamaged ships can move further than damaged ships.
• Visibility, radars and sonars:
  • All players essentially play on the same map, so if an opponent's ship gets close to yours, that ship is detected (and so is yours).
  • If a ship moves into an enemy's radar range, users get notified that something is there though they may not be told exactly what is there.
  • Submarines are invisible to radars, but are visible to sonars. Sonars may get confused by other stuff in the ocean (e.g., whales).
• Islands:
  • Islands hold hidden resources that you can use to buy new weapons and repair your ships.
  • Islands may a harbor to repair ships. A harbor may be neutral (all players can use it), or be player-owned (only the owner's ships can be repaired and restocked there). A player-owned harbor may be destroyed or conquered by the opponent.
  • One has a shop to buy bigger weapons. Newly bought weapons must be moved to a ship that can fire them before they can be used.
  • Stationary radars and forts may be built on islands. Both can be attacked by opponents.
  • ...
• Weapons:
  • Weapons have range, so you can only fire at a set of coordinates if you have a ship that is close enough to those coordinates.
  • Each type of ship is equipped with some special type of weaponry that allows for extra firepower, e.g., missiles that scatter, missiles with longer range, mines, and so on.
  • Supply ships may be used to transport special weapons to the ships that can fire those weapons, so that those ships do not have to sail to the harbor themselves. Supply ships are slow, and cannot defend themselves.
  • Decoy ships. Phantom ships intended to fool radars
• ...

In theory, there could even be communities of players playing against each other, building their own harbors (smart contracts of a certain standard that other players can interact with or even attack ...)

Which features does Battleship Royal need?

• Ability to execute smart contracts, private and public
• Ability to prove the correctness of one's move to the blockchain without revealing knowledge about the move itself (client-side proofs)
• Ability to store NFTs in the account itself (others should not see your weaponry)

Design ideas for a simple PoC

A lot of the necessary features come for free in Miden. Miden is built for client-side proofs and private, hybrid, and public smart contract execution. And in Miden, NFTs and other assets are being stored with the account itself. This means they are not visible for observers if the account stores its data locally. (see Miden State Model and Miden Privacy Model)

There could be one game smart contract represented by an account. All ships are accounts as well that have certain weapon NFTs in their vault. Ships store their position locally in their account itself; however, the game smart contract checks for the validity of changes in those coordinates.

Ship Accounts encode their move into a note, e.g., where to shoot at, where to move, ..., and send the note to the game smart contract.

The game smart contract could consume all incoming notes every hour to update the public game state and send notes back to the individual ships with their updates, e.g., being hit, radar notification, or repairment.