Ephemera

A photorealistic space exploration game in Unreal Engine 5.8, built with Claude Code. Walk around Dawnhollow, an Iceland-like ocean planet of moss-covered lava, basalt cliffs and black-sand coves, use your jetpack, and fly out to its moon.

Note: This is an early work in progress, free to play, and not really a game yet. There's no game loop: no goals, story, missions, progression, enemies or win/lose state. Right now it's a walking and flying sandbox, and the focus has been on getting the graphics and environment as good as possible (terrain, lighting, sky, volumetric clouds, a simulated ocean, aurora, views from orbit), plus the feel of the controls, the jetpack and the sound.

Download (Windows)

Get the latest release from the Releases page. Download both files into the same folder, then run the .exe:

• Ephemera-Setup-<version>.exe (the installer)
• Ephemera-Setup-<version>-1.bin (the game's data; it must sit next to the installer)

It installs for your user only, with no administrator prompt. The installer isn't code-signed, so Windows may show "Windows protected your PC". Click More info, then Run anyway.

Requirements: Windows 10/11 64-bit and a DirectX 12 graphics card. It's developed and tested on an RTX 3060.

Controls

Screenshots

All in-game, rendered in real time in Unreal Engine 5.8.

Space

On the surface

Source code

The full source is here, under the MIT licence (see LICENSE), so anyone can learn from it, improve it and build on it.

• unreal/Source/: the game's C++ (Unreal Engine 5.8): the solar system, gravity and reference frames, the player and jetpack, sky, sea, sound and UI.
• unreal/Tools/: the Python and shell tools that build the game's content from scratch: terrain generation, materials and shaders (build_slice.py), wave and sound bakes, packaging and the installer.
• unreal/Config/, unreal/Ephemera.uproject: the Unreal project.
• docs/unreal/DIRECTION.md: the design and technical decisions, and why. docs/research/: the research notes behind them.

Not included: the imported assets (Content/, several GB), which the tools rebuild. Textures come from Poly Haven (CC0, re-downloaded by unreal/Tools/fetch_polyhaven.py). The sound recordings come from the Sonniss GDC Game Audio Bundles, which are free to download but may not be redistributed as files, so they aren't here: unreal/SourceAssets/audio/CREDITS.md lists which ones are used. See unreal/README.md for building it.

Credits

• Textures and surfaces: Poly Haven (CC0).
• Sound: recordings from the Sonniss GDC Game Audio Bundles, plus CC0 footsteps from OpenGameArt and Kenney.
• Built with Claude Code.

Inspired by Outer Wilds. This is a non-commercial fan project with its own worlds, art and code; it doesn't use any of the original's assets or code.