This update is already available on the Stable branch, with 0.21.1 Stable 5 full release coming within a couple days.

This update focuses on internal systems: the new world generator, gameplay impacting weather and insolation, logic and trains have been reworked at the engine level. Right now, a multiplayer beta is already available.
The headline of this update is multiplayer. It already works: you can open your game for online play or join an existing one through Steam and build a base together.
Map generation got a rework. Terrain height is now driven by biomes, mountains and hills have been added, transitions between biomes are smoother, vegetation spawns in clusters, and grass loading has changed. New settings have been added, and the map can be changed radically without changing the seed.
Trains are in active development. The groundwork is already done — multi-car, stations, schedules.
On the logic side: a new interface, bugfix, almost all blocks support logic control.
For building: a surface leveling tool, an undo/redo, and Z-offset for blocks when placing them.
The boxes during construction have been removed, and a resource accessor snapping system has been added, making it much easier to connect blocks.

Weather got better — wind, humidity, rain post-processing, sky colors, clouds, stars and thunderstorms. Materials were reworked: polished steel looks better, platforms have correct roughness, copper and metals are less shiny. Machine consumption and production display was reworked and should no longer diverge from the descriptions; power consumption now shows in tooltips.
I spent a lot of time creating the second version of the questbook/training. Something similar existed before, but now the system is more sophisticated and interactive.
I hope to be able to turn this questbook into a full-fledged guide through the entire game; for now, it covers the bare essentials.
We'll now take some time to polish these systems and conduct playtesting, after which we'll release the game to the Default branch. The next big steps are refining trains and transport, drones, and interplanetary travel.
If you want to report a bug, suggest a game change, or ask a question — join us on Discord
