Sky City
An open-world driving and flying game built in Unreal Engine 5.8. The Chicago Loop and lakefront are stitched to downtown Austin, with a Texas rocket test site on the side. Drive, boost, wall-ride and fly the Skyster Roadster through all of it.
Sky City grew out of the browser game Skyster and is now a native Unreal Engine app. Its source is open to read, change and share for noncommercial use (it's source-available, not open source in the strict sense), and we'd love your help building it.
Status: early and playable. Apple Silicon Macs only for now. Expect rough edges.
Play it
Download the latest build from itch.io. It's free, signed and notarized.
You need:
- An Apple Silicon Mac (M1 or newer). UE 5.8 no longer renders on Intel Macs.
- About 6 GB of free disk space.
- An Xbox controller (recommended) or keyboard.
A Windows build is planned. If you have a Windows PC and want to help make it happen, see Contributing.
What's in the game
| Part | Status |
|---|
| Sky City map: about 3.6 × 3.6 km of Chicago + Austin, streets generated from OpenStreetMap | Playable |
| The L: Chicago's elevated Loop, a South line, 7 stations, a drivable deck | Done |
| Landmarks: fountain, pier and wheel, the Texas Capitol, more on the way | Partly done |
| McGregor maps (day and night): the rocket test site and the Roadster reveal | Playable |
| Traffic: ground cars and flying cabs, with signals | Playable |
| Game systems: self-driving mode, mini map, chargers, pickups, 6 levels, Garage | Playable |
Where it's heading: a Hot Wheels-style Course Builder (with an MCP server so your LLM can build courses for you), a Car Designer, easter eggs, achievements, races, and a story in which the player makes flying cars possible. See Design/ROADMAP.md.
Build from source
Requirements
- Apple Silicon Mac
- Unreal Engine 5.8 from the Epic Games Launcher (built and tested with 5.8.3)
- Xcode 26 (tested with 26.5) for compiling the C++ module. Xcode 26 installs the Metal compiler separately:
xcodebuild -downloadComponent MetalToolchain
- Git and Git LFS
- A free Epic Games account, to download City Sample (see below)
Steps
git lfs install
git clone https://github.com/kennyhassmusic/sky-city.git
cd sky-city
git lfs pull
The art (about 2 GB) comes from Sky City's own download server on Cloudflare, set in .lfsconfig, so cloning costs nobody anything and there's nothing extra to configure.
- Add the City Sample buildings. They are Epic's content and can't live in this repo, but they're free on Fab. Follow docs/SETUP_CITY_SAMPLE.md.
- The generated city is already in the repo, so there's nothing to run first. To change it, edit the generator scripts in
Scripts/ and rerun them (see CLAUDE.md for how the scripts are run). The city mesher is pinned to Blender 5.2.x LTS on Python 3.13 (tested on 5.2.3). It prints bpy.app.version at startup and stops on any other series. One Blender unit is one metre, and the glTF export is 1:1. primitive_cube_add's size is the full edge length (a size of 2 is a 2 m cube). Run it headless so a Python error cannot exit 0. A Python warning, a deprecated-API message, or a missing node or socket fails the build:
blender --background --factory-startup --python-exit-code 1 -P Scripts/city/blender_city.py
- Open the project: double-click
SkyCity.uproject and let the editor compile the C++ module. Open the SkyCityMashup map for the city, or McGregor / McGregorNight for the test site.
What's in this repo, and what isn't
| In the repo | Not in the repo |
|---|
| All game C++ code | Unreal Engine itself (install it from Epic) |
| City generation scripts (Python and headless Blender) | City Sample buildings (download from Fab) |
| The Roadster and original landmark models | Third-party vehicle models we can't redistribute (the repo has blocky stand-ins of the same size) |
| CC0 textures and props | Packaged game builds (those go on itch.io) |
| OpenStreetMap-derived street data | |
Contributing
Anyone can contribute: code, 3D models, landmarks, bug reports, playtesting. Start with CONTRIBUTING.md, then look for issues labelled good first issue.
Working with an AI assistant? Hand it AGENTS.md first: setup, the folder map, the rules and what to work on, in one file.
Want to reuse the art in your own project? Download the free Sky City Art Pack from itch.io (noncommercial use with credit; see docs/ART_PACK.md). You don't need it to contribute: git clone already gets the art.
High-value help right now:
- Original vehicle models (sedan, crossover, pickup, semi) to replace placeholder third-party models
- Landmarks and Austin sights built from public references
- A Windows build, if you have a Windows PC
How the team is organised, and how contributors become collaborators, is in GOVERNANCE.md. Please also read the Code of Conduct.
Licences
Free for everyone to play, mod, share, stream (monetized videos too) and contribute to. The only thing reserved is selling the game itself: only Kenny Hass Music LLC may do that.
| What | Licence |
|---|
| Code | PolyForm Noncommercial 1.0.0 |
| Original art and models (except as noted below) | CC BY-NC 4.0 |
| Street data derived from OpenStreetMap | ODbL: © OpenStreetMap contributors |
| The Sky City and Skyster names, logos, and the Roadster design | All rights reserved: see LICENSE-ASSETS.md |
| Third-party content | Its own licence: see CREDITS_AND_LICENCES.txt |
| Your contributions | You keep the copyright and license them to the project under the CLA |
Sky City is built with Unreal® Engine. Unreal and its logo are Epic Games' trademarks or registered trademarks in the US and elsewhere.
Disclaimer
Sky City features real-world cities and places as its setting. It is a fan-made game. It is not affiliated with, sponsored by, or endorsed by any company, landmark owner, artist, or government body.
