XSpaceWar-AI: We Rebuilt Spacewar! With Real Gravity — and It's Free

Sixty-four years ago a couple of MIT hackers wired two spaceships and a star into a PDP-1 and invented the multiplayer video game. We took that idea, gave it honest Newtonian physics, generated every pixel and every sound from math, taught the bots to be genuinely mean, and put 16 ships in the same arena. It’s done, it runs on Windows, macOS, and Linux, it’s Apache-2.0 open source, and it costs nothing.

👉 Play it now on itch.io — or grab a build straight from GitHub Releases.

The first networked match said everything

Dedicated server on one machine, two pilots joining from two more. The human — barely moving, just letting the star do the work — beat the AI 3 to −19, while the bot fell into the gravity well fifty-nine times. Newtonian gravity is undefeated.

The first networked deathmatch — human beats the AI 3 to −19

That score isn’t a difficulty setting. It’s physics. The star pulls with pure G·M / r² — no caps, no clamps, no softening. Fly too close and the pull genuinely diverges; you cannot thrust your way out of a star you’ve already fallen into. That’s not a bug, it’s a star.

The gravity well claims another ship

What it actually is

A modern, top-down space-fighter with a heavy AI focus — a 2026 reimagining of the classic networked Spacewar! / xspacewar. Bird’s-eye view like the 1962 original, but built in Godot 4 with:

  • Honest Newtonian flight. Conserved momentum, inverse-square gravity on ships and torpedoes, gravity-assist slingshots, hyperspace. No drag — to slow down you flip 180° and burn against your own velocity, the same maneuver Spacewar! pilots have flown since ‘62.
  • 100% procedural everything. Stars, planets, moons, asteroid fields, nebulae, ships, VFX — and audio. There’s not a single hand-drawn art asset or recorded sound file in the game; every sound is synthesized from math at load. Every match is a fresh seeded arena.
  • Up to 16 ships, four game modes: Free-for-all, Team battle, AI bots (Rookie → Insane), and Movie Mode — an all-AI attract reel that regenerates a brand-new arena, roster, and teams every 30 minutes. Leave it running on a second monitor; it never plays the same match twice.
  • Multiplayer that works today. Host-authoritative netcode with client-side prediction and reconciliation, automatic LAN discovery, direct IP, and platform-agnostic internet play through the project’s own relay/master server — room codes, an online server browser, no port forwarding and no platform account required.
  • Seven UI languages, including right-to-left Arabic.

Standing on 64 years of shoulders

XSpaceWar-AI is a clean-room implementation, but it knows exactly where it comes from: Spacewar! (MIT, 1962, on the DEC PDP-1), the 1974 PDP-11 networked port, and Ron Frederick’s 1992 X11 xspacewar 1.2 — an early serverless networked game where peers shared state directly. Huge thanks to Ron (github.com/ronf), whose 1992 networked Spacewar is this game’s direct ancestor.

Get in a ship

The whole thing is free and open source under Apache-2.0. No launcher, no account, no telemetry, ~100 MB on disk.

  • Easiest: play in the browser or download from itch.io.
  • Prebuilt binaries: the zip for your platform on GitHub Releases (Windows, macOS universal, Linux x86_64).
  • From source: clone the repo, run ./install.sh (it fetches and SHA-512-verifies Godot 4.6.3 for you), then godot --path ..
  • Steam: coming soon.

macOS note: the build is ad-hoc signed but not notarized, so Gatekeeper may claim it’s “damaged.” It isn’t — right-click → Open, or xattr -dr com.apple.quarantine /path/to/XSpaceWar-AI.app. Full instructions are on the releases page.

Bring friends. Pick HOST — LAN skirmish, share a 4-letter room code over the internet, or just turn on Movie Mode and watch the bots feed themselves to the star. The gravity is real, the maps are infinite, and the source is yours.

🚀 Play XSpaceWar-AI →

Apache-2.0 · GitHub · Codeberg mirror. Dedicated to JVL. Proudly Made in Nebraska. 🌽

Written on June 14, 2026