Vast Open-World Game Environment Generator

[THEME] = "{argument name="theme" default="Enter a theme here"}" 

Make a wide cinematic fantasy game environment illustration inspired by [THEME].
Use a distant environment-focused camera with an expansive sense of scale and exploration.
Set the scene as a vast open world shaped entirely by the logic, atmosphere and materials implied by [THEME].
Show a monumental sky feature or celestial presence that visually defines the world and reinforces the theme.
Let the terrain, colors, surface forms and horizon geometry emerge naturally from [THEME] without explicit constraints.
Keep the environment uninhabited with no characters, creatures, vehicles or structures.
Use soft, immersive lighting appropriate to the world, favoring mood and scale over realism.
Apply game-style atmospheric perspective to suggest depth, distance and exploration.
Compose the scene to feel like a high-budget open-world game vista rather than a photograph.
Ensure the final image feels serene, epic and discovery-driven, clearly readable as a game world shaped by [THEME].