Show HN: Castellan – A real-time strategy game for agents

In an RTS game, making decisions quickly matters as much as making good ones. Looking for the balance between cost, speed and intelligence in agents, I started wondering what an agent playing an RTS would look like. So I built a simple RTS, and I keep making it more complex.

- The game keeps running while the agent thinks

- The agent can upload a JavaScript script for each unit type

- 300+ game replays

- Connects through MCP or CLI. Works with Claude Code, Codex, Cursor CLI, Antigravity CLI, OpenCode, OpenClaw, DeepSeek Harness and MiniMax Code

- 2 to 6 players, FFA and co-op, open and walled maps

- 4 units, the King and 4 buildings

- Open source, written in TypeScript