There are 3 subsystems

1. Stones (and minerals). The planet is from stone, heated in the center. Sometime erupting and creating a volcano.
2. Plant kingdom. A hexagon based top layer, which procedurally grows plants. Plants have special conditions to grow and they create ecosystems. The plant change form according to day/night cycle. And they can be artificially kept in a day form by surrounding them with light, or in night form by surrounding them with darkness.
3. Creatures. Contrary to plants, creatures don't change form in day/night cycle. They are either dark or light creatures, which thrive each it its own realm. Dark creatures in the night, light creatures during the day. The emotions (light ↔ darkness) shape the plant kingdom. When creatures die, they become stones. Plants fruits are food for light creatures. Dark creatures consume energy of other creatures to live.

Plant kingdom of Nature is procedurally generated. And it is the main subsystem, which supports life.

Base hexagons tiling to cover all the planet.