Solana Game Preset

This game is ment as a starter game for on chain games. There is a js and a unity client for this game and both are talking to a solana anchor program.

This game uses gum session keys for auto approval of transactions. Note that neither the program nor session keys are audited. Use at your own risk.

To initialize the game preset with your own project name please use the command:

npx create-solana-game <name>

How to run this example

Quickstart

The unity client and the js client are both connected to the same program and should work out of the box connecting to the already deployed program.

Unity

Open the Unity project with Unity Version 2021.3.32.f1 (or similar), open the GameScene or LoginScene and hit play. Use the editor login button in the bottom left. If you cant get devnet sol you can copy your address from the console and use the faucet here: https://faucet.solana.com/ to request some sol.

Js Client

To start the js client open the project in visual studio code and run:

cd app 
yarn install 
yarn dev

To start changing the program and connecting to your own program follow the steps below.

Installing Solana dependencies

Follow the installation here: https://www.anchor-lang.com/docs/installation Install the latest 1.16 solana version (1.17 is not supported yet) sh -c "$(curl -sSfL https://release.solana.com/v1.16.18/install)"

Anchor program

Install the Anchor CLI
cd program to end the program directory
Run anchor build to build the program
Run anchor deploy to deploy the program
Copy the program id from the terminal into the lib.rs, anchor.toml and within the unity project in the AnchorService and if you use js in the anchor.ts file
Build and deploy again

Next js client

Install Node.js
Copy the program id into app/utils/anchor.ts
cd app to end the app directory
Run yarn install to install node modules
Run yarn dev to start the client
After doing changes to the anchor program make sure to copy over the types from the program into the client so you can use them. You can find the js types in the target/idl folder.

Unity client

Install Unity
Open the MainScene
Hit play
After doing changes to the anchor program make sure to regenerate the C# client: https://solanacookbook.com/gaming/porting-anchor-to-unity.html#generating-the-client Its done like this (after you have build the program):

cd program 
dotnet tool install Solana.Unity.Anchor.Tool <- run once
dotnet anchorgen -i target/idl/lumberjack.json -o target/idl/Lumberjack.cs

(Replace lumberjack with the name of your program)

then copy the c# code into the unity project.

Connect to local host (optional)

To connect to local host from Unity add these links on the wallet holder game object: http://localhost:8899 ws://localhost:8900

Video walkthroughs

Here are two videos explaining the energy logic and session keys: Session keys: https://www.youtube.com/watch?v=oKvWZoybv7Y&t=17s&ab_channel=Solana Energy system: https://www.youtube.com/watch?v=YYQtRCXJBgs&t=4s&ab_channel=Solana

Project structure

The anchor project is structured like this:

The entry point is in the lib.rs file. Here we define the program id and the instructions. The instructions are defined in the instructions folder. The state is defined in the state folder.

So the calls arrive in the lib.rs file and are then forwarded to the instructions. The instructions then call the state to get the data and update it.

├── src
│   ├── instructions
│   │   ├── chop_tree.rs
│   │   ├── init_player.rs
│   │   └── update_energy.rs
│   ├── state
│   │   ├── game_data.rs
│   │   ├── mod.rs
│   │   └── player_data.rs
│   ├── lib.rs
│   └── constants.rs
│   └── errors.rs

The project uses session keys (maintained by Magic Block) for auto approving transactions using an expiring token.

Energy System

Many casual games in traditional gaming use energy systems. This is how you can build it on chain.

If you have no prior knowledge in solan and rust programming it is recommended to start with the Solana cookbook Hello world example.

Anchor program

Here we will build a program which refills energy over time which the player can then use to perform actions in the game. In our example it will be a lumber jack which chops trees. Every tree will reward on wood and cost one energy.

Creating the player account

First the player needs to create an account which saves the state of our player. Notice the last_login time which will save the current unix time stamp of the player he interacts with the program. Like this we will be able to calculate how much energy the player has at a certain point in time.
We also have a value for wood which will store the wood the lumber jack chucks in the game.

pub fn init_player(ctx: Context<InitPlayer>) -> Result<()> {
    ctx.accounts.player.energy = MAX_ENERGY;
    ctx.accounts.player.last_login = Clock::get()?.unix_timestamp;
    ctx.accounts.player.authority = ctx.accounts.signer.key();
    Ok(())
}

#[derive(Accounts)]
pub struct InitPlayer<'info> {
    #[account(
        init,
        payer = signer,
        space = 1000, // 8+32+x+1+8+8+8 But taking 1000 to have space to expand easily.
        seeds = [b"player".as_ref(), signer.key().as_ref()],
        bump,
    )]
    pub player: Account<'info, PlayerData>,

    #[account(
        init_if_needed,
        payer = signer,
        space = 1000, // 8 + 8 for anchor account discriminator and the u64. Using 1000 to have space to expand easily.
        seeds = [b"gameData".as_ref()],
        bump,
    )]
    pub game_data: Account<'info, GameData>,

    #[account(mut)]
    pub signer: Signer<'info>,
    pub system_program: Program<'info, System>,
}

Chopping trees

Then whenever the player calls the chop_tree instruction we will check if the player has enough energy and reward him with one wood.

    #[error_code]
    pub enum ErrorCode {
        #[msg("Not enough energy")]
        NotEnoughEnergy,
    }

    pub fn chop_tree(mut ctx: Context<ChopTree>) -> Result<()> {
        let account = &mut ctx.accounts;
        update_energy(account)?;

        if ctx.accounts.player.energy == 0 {
            return err!(ErrorCode::NotEnoughEnergy);
        }

        ctx.accounts.player.wood = ctx.accounts.player.wood + 1;
        ctx.accounts.player.energy = ctx.accounts.player.energy - 1;
        msg!("You chopped a tree and got 1 log. You have {} wood and {} energy left.", ctx.accounts.player.wood, ctx.accounts.player.energy);
        Ok(())
    }

Calculating the energy

The interesting part happens in the update_energy function. We check how much time has passed and calculate the energy that the player will have at the given time. The same thing we will also do in the client. So we basically lazily update the energy instead of polling it all the time. The is a common technic in game development.

const TIME_TO_REFILL_ENERGY: i64 = 60;
const MAX_ENERGY: u64 = 10;

pub fn update_energy(&mut self) -> Result<()> {
    // Get the current timestamp
    let current_timestamp = Clock::get()?.unix_timestamp;

    // Calculate the time passed since the last login
    let mut time_passed: i64 = current_timestamp - self.last_login;

    // Calculate the time spent refilling energy
    let mut time_spent = 0;

    while time_passed >= TIME_TO_REFILL_ENERGY && self.energy < MAX_ENERGY {
        self.energy += 1;
        time_passed -= TIME_TO_REFILL_ENERGY;
        time_spent += TIME_TO_REFILL_ENERGY;
    }

    if self.energy >= MAX_ENERGY {
        self.last_login = current_timestamp;
    } else {
        self.last_login += time_spent;
    }

    Ok(())
}

Js client

Subscribe to account updates

It is possible to subscribe to account updates via a websocket. This get updates to this account pushed directly back to the client without the need to poll this data. This allows fast gameplay because the updates usually arrive after around 500ms.

useEffect(() => {
    if (!publicKey) {return;}
    const [pda] = PublicKey.findProgramAddressSync(
        [Buffer.from("player", "utf8"), 
        publicKey.toBuffer()],
        new PublicKey(LUMBERJACK_PROGRAM_ID)
      );
    try {
      program.account.playerData.fetch(pda).then((data) => {
        setGameState(data);
      });
    } catch (e) {
      window.alert("No player data found, please init!");
    }
 
    connection.onAccountChange(pda, (account) => {
        setGameState(program.coder.accounts.decode("playerData", account.data));
    });

  }, [publicKey]);

Calculate energy and show countdown

In the java script client we can then perform the same logic and show a countdown timer for the player so that he knows when the next energy will be available:

const interval = setInterval(async () => {
    if (gameState == null || gameState.lastLogin == undefined || gameState.energy >= 10) {
        return;
    }

    const lastLoginTime = gameState.lastLogin * 1000;
    const currentTime = Date.now();
    const timePassed = (currentTime - lastLoginTime) / 1000;

    while (timePassed > TIME_TO_REFILL_ENERGY && gameState.energy < MAX_ENERGY) {
        gameState.energy++;
        gameState.lastLogin += TIME_TO_REFILL_ENERGY;
        timePassed -= TIME_TO_REFILL_ENERGY;
    }

    setTimePassed(timePassed);

    const nextEnergyIn = Math.floor(TIME_TO_REFILL_ENERGY - timePassed);
    setEnergyNextIn(nextEnergyIn > 0 ? nextEnergyIn : 0);
    }, 1000);

    return () => clearInterval(interval);
}, [gameState, timePassed]);

...

{(gameState && <div className="flex flex-col items-center">
    {("Wood: " + gameState.wood + " Energy: " + gameState.energy + " Next energy in: " + nextEnergyIn )}
</div>)}

Unity client

In the Unity client everything interesting happens in the AnchorService. To generate the client code you can follow the instructions here: https://solanacookbook.com/gaming/porting-anchor-to-unity.html#generating-the-client

cd program 
dotnet tool install Solana.Unity.Anchor.Tool <- run once
dotnet anchorgen -i target/idl/lumberjack.json -o target/idl/Lumberjack.cs

Session keys

Session keys is an optional component. What it does is creating a local key pair which is toped up with some sol which can be used to autoapprove transactions. The session token is only allowed on certain functions of the program and has an expiry of 23 hours. Then the player will get the sol back and can create a new session.

With this you can now build any energy based game and even if someone builds a bot for the game the most he can do is play optimally, which maybe even easier to achieve when playing normally depending on the logic of your game.

This game becomes even better when combined with the Token example from Solana Cookbook and you actually drop some spl token to the players.

solana-developers/solana_game_preset

Solana Game Preset

How to run this example

Quickstart

Unity

Js Client

Installing Solana dependencies

Connect to local host (optional)

Video walkthroughs

Project structure

Energy System

Anchor program

Creating the player account

Chopping trees

Calculating the energy

Js client

Subscribe to account updates

Calculate energy and show countdown

Unity client

Session keys