Planet Gradius is located at a distance of 280,000 km from its star and its axis is kept substantially horizontal to it. For this reason, the northern hemisphere benefits from the star the entire year while the southern hemisphere stays in perpetual darkness for most of the year.
The planet has a population of about two billion people, as well as colony stars, called the seven neo-space plants, on its vicinity. Most of the Gradian population lives on the northern hemisphere, which became technologically advanced and is where the Empire's government resides. The southern hemisphere was originally only inhabited by the Wreek, who had to live a primitive lifestyle there due to being very susceptible to cosmic rays.