Star Apocalypse is the reinvention of the 4X genre. The game is a real time game of intergalactic civilization, using the computation power of modern computers to run advanced simulations on cultural, technological and societal interaction and development.
This is a gradient created from a planet's environmental stats. The amount of 'blue' (water) is dependent on the amount of water in the environment. The range of the snow area depends on the planet's temperature.
This makes sure that planets are fully procedural (planet textures get generated with a 'PRNG' pulled through a noise function).