The levels are generated randomly every time you die and restart, that is common part of the Roguelike game structure. Your objective is to complete each level and get to the end of level 6 to find your Beacon to escape the planet. Each level has extra loot objectives like Stockpiles that spawn Weapons and Caches that will give you Passive Items, and secrets where you can get bonus loot. Beacon is unique in the genre because of the Cloning system that allows you to apply DNA and gain Mutations after each death, giving you bonus stats and abilities for multiple lives.
Im pretty sure in the lore scattered around the place it mentions the mining operations and alien hives both expand very fast and if it takes a little while to grow a new clone it could explain why the terrain keeps changing
