Rimworld 1.0 came out so many people will ask for an update for Terra.
As you may already know, I'm currently working on a big update with new features. Development comes closer to a working alpha version, so it's time to present you what is coming. As you can see I'm planning to make most big features optinal, so players can choose if they want to play with it or not. This can be quite complicated for some systems, so it may come in a later update. Also mod compatibility patches with other mods will come later.

Many new biomes were added with unique map generators, including islands and caves.
Cold: cold deep bog, frozen lake
Temperate: temperate meadow, spike mountains, deep temperate swamp, tidal flats
Warm: deep tropical swamp, mangrove forest
Warm arid: savanna, oasis
High: desert high plains
Caves: cave oasis, tunnelworld cave, cave entrance, infested mountains, desert danyon
Islands: archipelago, tidal islands, volcanic islands, tundra skerries, pack ice, atoll

The biome generator code can be used from other mods to add more biomes or add content to existing biomes, most done in xml.
Especially the Biomes! mods will use this to add more unique and detailed content to Terra biomes (plants, animals, resources, items, ...).

The terrain now is an actual 3d terrain surface. It's not visible in the normal top-down view of the game, but a heightmap overlay shows the elevation of each cell. Natural terrain also has dynamic fertility and moisture levels that change through many different systems and interactions. On top water is also a dynamic element. Rainwater pours on the ground and wets the soil or flows to lower elevations and create a puddle and later a lake. The ocean is a large water body that rises and lowers by the tides, as well as rivers have their own system (both see below). There are also map overlays for the other dynamic parts to give a better overview on each property.
Of cource there are still some limitations on realism to make this run smooth on weaker computers. (And also because realistic terrain and fluid simulations are subject to current scientific research, so not really in the scope to add to a game mod.)

Water is dynamic as the terrain is, so water levels can change over time. There are many different smaller factors that change water levels in general, but oceans and rivers are affacted by their own bigger system.
Oceans:
Ocean water high is dependent on the tides. There is around 1 full tide each day. Depending on the biome, the water level and coastline can change a lot. Tidal flats and islands have the biggest change. Be especially careful when building near the cost on low land since there also can be storm surges.
Rivers:
Most of the year rivers have a normal water level. There are seasons and events where the level can change drastically from almost drying out to flooding the whole area.

There is natural grass growing on soil, a bit like the grass in Minecraft. It spreads and grows over time and gets destroyed on heavy used terrain. Colonists that walk the same path often, remove the grass and cut a tail in it. Thick grass layers reduce movement speed slightly while colonists can follow trails with their normal speed.

The dynamic terrain allows terraforming in a natural way: Want to create a lake? Put water there. Want desert to be fertile? Use fertilizer and green manure plants to enrich sand to soil.
There are various buildings, items and work types designed around this system. This is not "place the terrain you want from the floor menu and done". Terraforming is done by how it would be done normally. The focus hereby lies on changing soil properties (fertility, moisture, water level, grass layer). There is (currently) no way to change mountain to soil and there maybe will never for game design reasons.
Stuff you can do:
- Collect water from different sources (rain, lakes, soil moisture, groundwater)
- Irrigate soil and growing zones
- Fertilize soil with different kinds of fertilizer or green manure plants (later more about that)
- Destone terrain (change gravel to soil)
- Plow terrain for young plants to grow better
- Manage natural grass layer growth

Weather commonalities depend on the current season and biome. Spring and summer may be more clear with a rainy fall in a temperate region, while in the tropics the summer may be a rainy monsoon and winter is clear. Weather has a shorter duration and changes more often, so the impact of each current weather on the dynamic terrain is not too high. There also are new weather types, especially more rain and storm variants.

Plants have new properties like different moisture and temperature requirements and fertility and water consumption. To fill the resulting niches, more plants were added. Each tries to fit a specific purpose and has a valid use or unique advantage. So there are different plants that grow better in warm and dry or cold climate. Others have a long grow time but can be harvested many times once grown.
Green manure:
Plants can be dig in the soil to increase ground fertility. Some plants can accumulate lots of nutrients while growing and will improve the soil by a lot when dug into the soil.
Bees and blossoms:
You can place beehives near plants. Bees will collect pollen from plants and produce honey. Of course they prefer to collect pollen from nice blossoms and collect more from then than from other plants, so place then near your blooming crops and flower beets. Plants that have blossoms will also get an instant growth boost when a bee pollinates its blossom.
Intercropping:
Some plants like to grow next to other plants. IRL they protect each other from parasites or use nutrients more efficient. Here some plants get a small growth rate bonus or malus if they grow next to a plant they like or not. This system is meant as a minor bonus for player who want to invest more in detailed planning, but it is not needed to care about.
Plowing soil:
You can toggle a setting on growing soils that colonist should plow the soil before sowing a plant. Young plants get a good boost on their growth rate on plown soil. After harvesting, the soil becomes normal again and needs to be replown again.
New groing zones:
There are various new groing zones to make farming earier. You can use seasonal growing zones to create crop rotation plans and mixed zones for easy intercropping.
Plant waste and recycling:
When researched, colonists can gather the remains of cut plants and crops as plant waste to recycle. Build compost heaps to compost plant waste to fresh compost fertilizer. As an alternative you can also ferment plant waste to silage to feed your animals with it.

There is a new need "food variety" to encourage planting different kinds of food. It works somewhat similar to the recreation system, so the amount of needed food types to keep your colonists happy depends on the expectation level of the colony. This need only affects mood and doesn't reflects health issues from a one-sided diet. Meals also got a small rework to fit into this system. This need is basicly a more detailed replacement of "Ate lavish meal -12". There are 8 kinds of foods: basics, greens, vegetables, fruits, mushrooms, animal products, seafood, meat.

There are different ways to get food of the new food kind "seafoods".
Fish:
Place fishing spots and let your colonists fish. Catching rates depend on the water body, so don't you won't catch anything in a rain puddle.
Shrimps:
Build shrimps farms in the water to start farming shrimps. Shrimps grow over time in the farm and can be harvested from time to time. Be careful that the water level is always correct. Shrimps die from no water while too much floods the farm and part or the shrimps escape.
Mussels:
You can collect mussels from beaches. (still work in progress)

Grow mulberry trees and place silkworm breeders next to them to start farming valuable silk. Silkworms from the breeder go to nearby mulberry plants to pupate to cocoons which can be collected and refined at the loom to create silk cloth. Silk is very comfortable to wear, even more in the heat and also quite durable. It can also be sold with a good price.
Now cotton and devilstrand also yield raw plant material when harvested that needs to be spun to cloth at the loom.

Wild plant spawner rework:
Wild plants spawn in biomes also depending on the climate and not only the biome. So a temperate forest next to arid shrubland has less plants and a mix of temperate and arid plants while one next to a tropical forest has more plants and a mix of temperate and tropical vegetation.
This idea needs some testing how it will turn out. Since mixing vegetation removes the distinctiveness of a biome which may be bad.
Boats / ocean caravaning:
Adding boats to travel over the ocean. There are different concepts that need testing to see what is the best. One is more similar to how drop pod traveling works. Another is to carry a "boat item" and then do normal caravaning over the water.