This is not a complete game! Instead, this is a setting for Superfantasy, found here:

The planet Gigaia spins about its star, Zelus. It has no moon. Instead, it is encircled by a spectacular ring around its equator.

Creatures called “lightsworn” and “darkspawn” once came to Gigaia from faraway places. The lightsworn call their bright, crystalline paradise “Heaven”. The darkspawn name their inky-black sphere “Hell”. Now, these home planets sit on opposite sides of Gigaia, dominating the sky. Both are connected to Gigaia by atmospheric bridges, allowing sufficiently sturdy fliers to move from planet to planet.

Gigaia has become the battlefield in the eternal war between light and dark. Lightsworn ensconce their essence into fearfully beautiful shells called Angels. The darkspawn possess biomechanical devil-mecha called Demons. Each side crosses the atmospheric bridge to do battle with the other on land, sea, or sky.