Build Your First Summer Game

Multiplayer by default

The Summer SDK contract is multiplayer-native. The default example is host-authoritative: the server runs the rules, clients render synced state, and a min_players of 1 means the same build is also a solo game. You write SummerGame hooks and synced state in GDScript; the Summer SDK defines the creator-facing contract. The SDK/runtime surfaces on this page are scaffolded, not a deployed hosted gameplay path. Check platform capability status before making production promises. What you build here:

extends SummerGame,
server-authoritative gameplay updates (Summer.is_server()),
player-visible state via set_synced,
1–8 players from the same code path,
passes local testing and the submission pipeline.

Want an AI agent to run this whole page for you? Point it at /agent-setup — the prompt there contains a complete verified template (project files, local SDK stubs, export preset) and the publish calls.

Step 1: Create `manifest.json`

{
  "id": "first-summer-game",
  "name": "First Summer Game",
  "version": "1.0.0",
  "summer_sdk": "1.0",
  "entry_scene": "main.tscn",
  "player_scene": "player.tscn",
  "min_players": 1,
  "max_players": 8
}

min_players: 1, max_players: 8 is the multiplayer-native default — ship it unless your design demands otherwise. Paths are relative to the manifest at the pack root.

Step 2: Choose Your Player Path

3D Action Template (fastest start)

set player.tscn root script to res://sdk/summer_character_3d.gd
use apply_default_movement(...) from SummerGame.

Custom Genre Path (2D/card/RTS/puzzle)

make your own script extending SummerPlayer
sync your own state model (set_synced("hand_count", ...), etc.).

Either way the authority rule is identical: the server writes synced state, clients read it.

Step 3: Build `main.gd`

extends SummerGame

const ROUND_SECONDS := 120.0
const MOVE_SPEED := 7.0
const GRAVITY := 20.0

func get_prediction_params() -> Dictionary:
    return {"move_speed": MOVE_SPEED, "gravity": GRAVITY}

func _game_init() -> void:
    var spawn_root := get_node_or_null("SpawnPoints")
    if spawn_root:
        for child in spawn_root.get_children():
            if child is Node3D:
                spawn_points.append(child.global_position)

func _game_start() -> void:
    Summer.set_time_limit(ROUND_SECONDS)
    Summer.send_announcement("Round started")

func _game_end() -> void:
    Summer.send_announcement("Game over")

func _player_joined(player) -> void:
    if player.has_method("respawn"):
        player.respawn(get_random_spawn_point())
    player.set_synced("score", 0)

func _player_left(_player) -> void:
    pass

func _process(delta: float) -> void:
    super._process(delta)
    if not Summer.is_server():
        return
    for p in get_players():
        if p.has_method("respawn"):
            apply_default_movement(p, delta, MOVE_SPEED, GRAVITY)

Give main.tscn a SpawnPoints node with at least 4 child Node3D spawn markers and a Players node — the multiplayer defaults assume them.

Step 4: Add One Multiplayer Rule

Example scoring rule — note it runs only on the server path, and clients see it through set_synced:

func score_point(player) -> void:
    var current := int(player.get_synced("score") if player.get_synced("score") != null else 0)
    current += 1
    player.set_synced("score", current)
    Summer.send_announcement("%s scored (%d)" % [str(player.get("display_name")), current])

Step 5: Local Test

Start with the canonical one-process Summer Engine smoke checks. If your starter project includes the optional loopback runner, also use it to exercise a local server/client path:

the canonical agent prompt validates import, parsing, smoke execution, banned patterns, and pack contents with local SDK stubs;
the optional loopback runner starts a local headless server and connects a client to localhost;
neither path validates production platform services, ticket redemption, or hosted matchmaking.

Guide: Testing Your Game Locally. Building outside Summer Engine (agent/CLI workflow)? The same page covers stub-based validation, and the /agent-setup prompt automates it.

Step 6: Export and Publish

Export a game-only .pck, then publish it through the live release API (create game → presigned upload → server-verified finalize → manual review):

A human reviews every release. Approval assigns published catalog status and makes the release available under the documented authenticated download rules. Browser and desktop-shell play of uploaded Summer games are not live yet.

What “Done” Looks Like

All lifecycle hooks implemented.
Server authority enforced (Summer.is_server()).
Player-visible state comes from set_synced.
Works with 1 player and with several (min_players: 1).
Canonical Summer Engine smoke checks pass.
Optional local loopback runner passes when present.
Export contains only game files; release enters pending_review.

Previous: Create a Summer game

Return to project creation and the GDScript starting point.

Next: Choose Summer SDK capabilities

Use the lifecycle hub to select the SDK systems your game needs.

Start here

Summer SDK

Test and publish

Other ways to start

Essentials

Models

Using Summer

Summer Studio

Other Engine Migration

Automation

Reference

Build Your First Summer Game

Multiplayer by default

Step 1: Create `manifest.json`

Step 2: Choose Your Player Path

3D Action Template (fastest start)

Custom Genre Path (2D/card/RTS/puzzle)

Step 3: Build `main.gd`

Step 4: Add One Multiplayer Rule

Step 5: Local Test

Step 6: Export and Publish

What “Done” Looks Like

Previous: Create a Summer game

Next: Choose Summer SDK capabilities

​Multiplayer by default

​Step 1: Create manifest.json

​Step 2: Choose Your Player Path

​3D Action Template (fastest start)

​Custom Genre Path (2D/card/RTS/puzzle)

​Step 3: Build main.gd

​Step 4: Add One Multiplayer Rule

​Step 5: Local Test

​Step 6: Export and Publish

​What “Done” Looks Like

Previous: Create a Summer game

Next: Choose Summer SDK capabilities

Multiplayer by default

Step 1: Create `manifest.json`

Step 2: Choose Your Player Path

3D Action Template (fastest start)

Custom Genre Path (2D/card/RTS/puzzle)

Step 3: Build `main.gd`

Step 4: Add One Multiplayer Rule

Step 5: Local Test

Step 6: Export and Publish

What “Done” Looks Like