> ## Documentation Index
> Fetch the complete documentation index at: https://summer-18f03259-codex-native-multiplayer-entry.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# Guide: Making A 2D Game Multiplayer

> Integrate Summercraft into a 2D game by extending SummerPlayer and syncing your own state.

## Platform Framing

You are building a 2D **Summer game** in **GDScript** and integrating the **Summer SDK**
platform contract:

* host-authoritative game rules and synced state,
* player, data, economy, teams, and score interfaces,
* a submission contract for review.

The hosted multiplayer runtime, automatic matchmaking, and player-facing play surfaces are
not production-live yet. See the canonical
[platform capability status](/knowledge-base/source-status#platform-capability-status).

## Recommended Player Model

For 2D games, create your own 2D player class that extends `SummerPlayer`.

```gdscript theme={null}
extends SummerPlayer

@export var speed := 220.0
var local_position := Vector2.ZERO
var is_alive := true

func _ready() -> void:
    set_synced("x", local_position.x)
    set_synced("y", local_position.y)
    set_synced("anim", "idle")
```

## Server Authority Loop

```gdscript theme={null}
extends SummerGame

func _process(delta: float) -> void:
    super._process(delta)
    if not Summer.is_server():
        return

    for p in get_players():
        _step_2d_player(p, delta)

func _step_2d_player(player, delta: float) -> void:
    var move: Vector2 = player.input.movement
    player.local_position += move.normalized() * player.speed * delta

    player.set_synced("x", player.local_position.x)
    player.set_synced("y", player.local_position.y)
    player.set_synced("anim", "run" if move.length() > 0 else "idle")
```

## Client Render Pattern

On clients, render from synced state:

```gdscript theme={null}
func _process(_delta: float) -> void:
    var x = get_synced("x")
    var y = get_synced("y")
    if x != null and y != null:
        $Sprite2D.global_position = Vector2(float(x), float(y))
```

## Joining / Leaving

```gdscript theme={null}
func _player_joined(player) -> void:
    player.set_synced("x", 0.0)
    player.set_synced("y", 0.0)
    player.set_synced("hp", 100)

func _player_left(player) -> void:
    pass
```

## Optional Subsystems

Use only what you need:

* `Summer.score` for score/rank,
* `Summer.teams` for team modes,
* `Summer.data` for persistent inventory/progress,
* `Summer.economy` for currency.

## Common Mistakes

* Running movement authority on clients.
* Mutating score/economy from client paths.
* Treating `set_synced` as client-owned state.

## Production Checklist (2D)

* [ ] `Summer.is_server()` gates all authoritative state updates.
* [ ] 2D state is synced via `set_synced`.
* [ ] Client only renders synced values.
* [ ] Required manifest fields valid.
* [ ] Canonical Summer Engine smoke checks pass.
* [ ] Optional local loopback runner passes when present.