Forge ECS

A Rust game engine built on the Entity Component System (ECS) design pattern, with a wgpu renderer, winit windowing, and an imgui debug UI.

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Architecture Diagrams

1) Multiplayer networking (matchmaking + peer-to-peer gameplay)

flowchart LR
    PEERS["Game peers (players)"] -->|"Create/Join lobby"| MM["Matchmaker"]
    MM -->|"MatchStart + endpoints"| HOST["Host peer"]
    MM -->|"MatchStart + endpoints"| CLIENT["Client peer(s)"]
    CLIENT -->|"Input"| HOST
    HOST -->|"Replicated state / corrections"| CLIENT

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2) ECS update model and graphics rendering path

flowchart TD
    LOOP["Event loop"] --> UPDATE["Update systems"]
    UPDATE --> WORLD["World state"]
    WORLD --> DRAW["Build draw commands"]
    DRAW --> RENDER["Render frame (wgpu + optional imgui)"]

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Multiplayer demo (quick start)

# terminal 1: matchmaker (listen on all interfaces)
cargo run --bin matchmaker -- --bind 0.0.0.0:7000

# terminal 2: player client (launcher UI)
cargo run --bin game 
# optional: override default gameplay UDP port (default is 7001)
cargo run --bin game -- --game-port 7010

Enter 127.0.0.1:7000 as the matchmaker address and click "Connect", then proceed to create or join a lobby. If the client runs on another machine, replace 127.0.0.1 with the matchmaker host's LAN IP.

Firewall setup for LAN multiplayer (Windows + Linux)

The demo uses UDP:

• 7000 for matchmaker
• 7001 for gameplay peers by default (--game-port changes this)

Open these ports on every machine that hosts matchmaker or runs a player client.

Windows (PowerShell as Administrator):

netsh advfirewall firewall add rule name="Forge Matchmaker UDP 7000 In" dir=in action=allow protocol=UDP localport=7000 profile=private
netsh advfirewall firewall add rule name="Forge Matchmaker UDP 7000 Out" dir=out action=allow protocol=UDP localport=7000 profile=private
netsh advfirewall firewall add rule name="Forge Gameplay UDP 7001 In" dir=in action=allow protocol=UDP localport=7001 profile=private
netsh advfirewall firewall add rule name="Forge Gameplay UDP 7001 Out" dir=out action=allow protocol=UDP localport=7001 profile=private

Linux (ufw):

sudo ufw allow 7000/udp
sudo ufw allow 7001/udp
sudo ufw reload

Linux (firewalld):

sudo firewall-cmd --permanent --add-port=7000/udp
sudo firewall-cmd --permanent --add-port=7001/udp
sudo firewall-cmd --reload

If you run clients with a non-default gameplay port, open that UDP port instead of 7001.

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Running the demo

cargo run --bin demo

Requires a working GPU with Vulkan, DX12, or Metal support.

The demo opens a 1280x720 window showing two oscillating shapes:

• An orange circle on the left
• A blue rectangle on the right

The "Entity Colors" imgui window (top-left) lets you:

• Edit RGBA colors for each shape live
• Adjust oscillation frequency (0.1 - 5.0 Hz)
• Adjust oscillation amplitude (10 - 400 px)