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Let’s eat. I feel like our strange circles floating around their empty abyss are probably getting hungry by now…


For this I’m deliberately going to leave out simple code snippets since you should now have a good enough understanding to be able to add the easy bits yourself. If you’re struggling, go back and look through the previous chapters and the code you’ve already written and, if all else fails, look it up in the complete project.

Add a new C# file to our server plugin called “AgarFoodManager” and make the class a DarkRift plugin (first challenge!). Make sure you set ThreadSafe to false so you don’t have problems later!

Add a HashSet field called food that contains FoodItem objects and initialise it empty. Add the following definition of FoodItem to a new file:

public class FoodItem : IEdible
    public ushort ID { get; set; }
    public float Radius => 0.1f;
    public float X { get; set; }
    public float Y { get; set; }

    public byte ColorR { get; set; }
    public byte ColorG { get; set; }
    public byte ColorB { get; set; }

    public FoodItem(ushort ID, float x, float y, byte colorR, byte colorG, byte colorB)
        this.ID = ID;
        this.X = x;
        this.Y = y;
        this.ColorR = colorR;
        this.ColorG = colorG;
        this.ColorB = colorB;

Now add the following definition of IEdible to a new file and make Player implement the IEdible interface (see where this is going?).

public interface IEdible
    ushort ID { get; }
    float X { get; }
    float Y { get; }
    float Radius { get; }

In the food manager constructor add a number of food items (I did 20) with random values to the food HashSet similarly to how we assigned values to the players. For the ID field just assign them incrementing values from 0 so we can identify then uniquely later.

Now for a more challenging part! Make it so that when a player connects to the server the AgarFoodManager sends the latest positions of all food to the new client, ideally this should be in one message as we did before with the players (hint!) but if you’re struggling just implement it as 1 message per food item and get that working first. Create a dedicated food spawn tag for this.

Switching to the Unity project, add a FoodManager MonoBehaviour and attach it to the Network object. In this script, you’ll need to pass in the client and receive the list of food that the server sends, again you can probably reuse some of the player code here. Make sure you track the food items you add using a dictionary (ID as key) so that we can access them later.

You should be able to test now and see lots of food appear on the map with your players!

While we’re testing, add some code to set the CameraFollow.Target on our main camera to our player so that it follows them around.

Let’s switch back to AgarPlayerManager and add in some code to actually eat the items of food! In our MovementMessageReceived method add the following code:

player.X = newX;
player.Y = newY;

AgarFoodManager foodManager = PluginManager.GetPluginByType<AgarFoodManager>();

foreach (FoodItem food in foodManager.Food)
    if (Math.Pow(player.X - food.X, 2) + Math.Pow(player.Y - food.Y, 2) < Math.Pow(player.Radius, 2))
        player.Radius += food.Radius;

It should be fairly easy to make out the Pythagoras in there. Essentially, we’re just checking the distance between the food and the player is less than the player’s size in a makeshift collision routine, we can then increase our player’s size appropriately and “eat” the food.

This won’t compile yet because there’s three missing items; before we add them, let’s look at the GetPluginsByType call. Since DarkRift handles the instantiation of plugins you can’t get a reference to other plugins without querying DarkRift because DarkRift is the entity with that reference so that’s exactly what we do here.

Hopefully you can see that the Food property and the Eat method need to be implemented in the AgarFoodManager class so add the following line:

public IEnumerable<FoodItem> Food => food;

The SendRadiusUpdate function should send a message containing the new radius to every client using a radius update tag, you’ll also need to check the tag in NetworkPlayerManager on the client and either call SetMovePosition or SetRadius on the AgarObject so it does the right action!

Lastly, have a go at implementing the Eat method. All this needs to do is move the item of food to another, random location and inform all connected clients of this. Add yourself another tag value for issuing the move command.

The only thing that needs adding on the client now is some code to handle the movement of food items, everything else is already handled by the server side logic! Have a go at adding it yourself.

If you have trouble with the collisions not lining up with your graphics try adjusting the scale value on the AgarObjects.