Biomes
The full release shipped new scenarios across diverse biomes, and an achievement requires visiting all biomes. The store page does not enumerate them by name, and neither does the announcement feed — the official copy consistently speaks of biomes and maps without listing them. Treat any named list of Wall World Strategy biomes you find online as unverified until Alawar publishes it.
What the official material does confirm is that different environments change what you are dealing with. The expedition section describes hostile environments, unstable terrain and unknown lifeforms as things you prepare for, and the depths are described as a separate world beneath the surface with its own resources and artefacts. A different biome is a different expedition, not a reskin.
Sandbox mode lets you choose from different maps and difficulty levels and tailor the conditions to your liking. The map is the variable you select; the biome is what you encounter within it.
Multiple difficulty settings shipped in the full release, and the campaign has three named tiers with their own achievements: Light, Medium and Hard. Since Sandbox lets you tailor conditions yourself, difficulty is a dial rather than a single ladder.
In Sandbox you develop your colony without story constraints or time pressure. Zyrex will still attack, but you play at your own pace and experiment with different development and defence strategies. It is the mode to learn the building and research systems in, since the failure states do not cost you a campaign.
The full release added new challenges and dynamic events alongside the biomes and difficulty settings. These are the emergency events — accidents, disasters, environmental hazards — and the store page is explicit that they do not destroy the colony instantly but instead disrupt operations and trigger cascading problems. Difficulty comes from accumulation, not from a single hit.