How to Build Local Multiplayer in Unity (Architecture, Input & Camera Systems)

Welcome to Local Space.

Hi everyone, I hope you're all doing well. While I try to keep these posts evergreen I just wanted to say that building local multiplayer this year has felt different. There’s something special about designing games where people share the same couch, the same screen, and sometimes the same arguments. It forces clarity. It exposes weak systems instantly. And it reminds you why games are fun in the first place.

Feel free to jump on discord and tell me what you're building. I love seeing couch co-op and arena prototypes coming together.

If you are new here, this is my recurring dev log. I spend my week building in Unity, figuring out how to make things work, and inevitably breaking them. Then, I share the notes, tools, and code snippets that actually survived the process.

In this log, we are diving into something I care deeply about: Local Multiplayer Architecture in Unity. Not just “how to get two controllers working,” but how to build systems that scale cleanly from 2 players to 4 without turning your project into spaghetti.

1. Input Is a System, Not a Script (Technical Deep Dive)

Most beginners wire input directly into their PlayerController and call it a day. That works for one player. It collapses under four.

In local multiplayer, input must be instance-driven. Every player needs its own input context, bindings, and device ownership.

Core Principle: The Player owns its Input. The Game does not.

[RequireComponent(typeof(PlayerInput))]
public class PlayerController : MonoBehaviour
{
    private PlayerInput playerInput;
    private Vector2 moveInput;

    private void Awake()
    {
        playerInput = GetComponent<PlayerInput>();
    }

    public void OnMove(InputAction.CallbackContext context)
    {
        moveInput = context.ReadValue<Vector2>();
    }

    private void Update()
    {
        Move(moveInput);
    }

    private void Move(Vector2 input)
    {
        Vector3 direction = new Vector3(input.x, 0f, input.y);
        transform.Translate(direction * 5f * Time.deltaTime);
    }
}

Technical Deep Dive: When using PlayerInputManager in Join Players Manually mode, Unity automatically pairs devices to spawned prefabs. This keeps your architecture modular. No static references. No global input polling. Each player becomes a self-contained system.

This is the difference between a prototype and a scalable foundation.

2. Camera Framing Is Game Feel (Systems Spotlight)

Local multiplayer fails when players fall off-screen. The camera is not just visual polish. It is gameplay infrastructure.

The Pattern: Use a dynamic target group that adjusts framing based on active players.

Instead of parenting the camera to Player 1, track all live players and compute bounds.

public class TargetGroupManager : MonoBehaviour
{
    public CinemachineTargetGroup targetGroup;

    public void RegisterPlayer(Transform player)
    {
        targetGroup.AddMember(player, 1f, 2f);
    }

    public void UnregisterPlayer(Transform player)
    {
        targetGroup.RemoveMember(player);
    }
}

If you want a stable default frame when no players exist, add a central platform anchor as a fallback target. This prevents awkward zoom spikes.

When you build this properly, the camera stops feeling like a utility and starts feeling like part of the combat system itself. In the Bootcamp course, we build this step by step so you understand why each piece exists instead of just copying a prefab.

3. Events Over Direct References (Architecture Pattern)

Four players mean four death states, four respawns, four elimination triggers. Hard references become brittle quickly.

Game Architecture Principle: Let players broadcast events. Let systems listen.

public class PlayerHealth : MonoBehaviour
{
    public static event Action<PlayerHealth> OnPlayerDied;

    public void Die()
    {
        OnPlayerDied?.Invoke(this);
        gameObject.SetActive(false);
    }
}

Now your UI, camera system, score manager, and respawn logic can subscribe independently. No tight coupling. No circular dependencies.

This is especially important in couch co-op where state changes happen constantly and unpredictably.

4. Designing for Shared Space (Game Design Theory)

Local multiplayer is physical. Players lean, shout, grab controllers, and sometimes obscure the screen with their heads. That means:

• UI must be readable at distance.
• Player silhouettes must be distinct.
• Feedback must be exaggerated.

Subtle design works in single-player. In local multiplayer, subtle gets lost in noise.

The Rule: If a hit lands, everyone in the room should feel it.

If you are serious about building local multiplayer games that survive real-world testing, structured systems matter. That’s the entire philosophy behind how I designed the Bootcamp curriculum.

5. The "Couch Test" (Business of Indie Dev)

Before you polish menus. Before you tweak shaders. Before you build a progression system.

Run the Couch Test.

Put four people in a room. Hand them controllers. Do not explain anything. Watch silently.

• Do they understand how to join?
• Do they know who they are?
• Do they laugh?
• Do they argue?

If they argue about the game, you are onto something.

If they argue about the controls, you have work to do.

// When you are ready

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