Scenario system
New scenario system allows you to choose, randomize, and customize special situations to play in. Determine starting situation, your type of community (tribe, colony), permanent map conditions, starting items, animals, health conditions, and traits, and change special rules.
Several built-in scenarios, including one matching the classic RimWorld experience, are included.
You can randomize new scenarios.
You can customize scenarios with a special interface that allows creation of any scenario you like.
Scenarios can be uploaded to or grabbed from Steam Workshop with a single click.
ScenPart: Permanent version of all map conditions (eclipse, solar flare, etc).
ScenPart: Planetkiller scenario part: World is destroyed on X date.
ScenPart: Climate cycle which makes the world get warmer and cooler over a period of years. Winter is coming.
ScenPart: Disable building a given type of building.
ScenPart: Pawns start with health condition.
ScenPart: Start with items.
ScenPart: Map is scattered with items.
ScenPart: Configure arrival method (pods or standing)
ScenPart: Starting pawns are all between ages X and Y
ScenPart: Pawns explode on death (configurable type and radius)
ScenPart: All pawns from source (game start/all) have trait X
ScenPart: Starting animal(s)
ScenPart: Disallow mining
ScenPart: Disallow hunting
ScenPart: Disallow taming
ScenPart: Disallow growing
ScenPart: Disable incident
ScenPart: Multiplier for any stat on the game (move speed, mining speed, etc)
ScenPart: Disallow building
Pawn overlapping
Pawns can no longer overlap during melee combat (unless they're really small). No more animal deathstacks! This also creates new tactics around blocking, surrounding, or back-line shooters. We had to write a bunch of AI and blocking code to make this function.

AI
Raiders can now enter "steal" mode if they see enough value. They'll grab your stuff and carry it off.
Kidnapping raiders now work together much better to kidnap. Instead of everyone fleeing at once, some will kidnap while others cover them.
AI dressing algorithm is now better at making outfits to withstand cold temperatures. If there is no way to make a survivable outfit, pawns won't arrive at all. No more raids arriving and keeling over in -60C weather.
Predators no longer hunt boomrats and boomalopes.
Pawns will be smarter about avoiding traps in various situations.

New stuff
Full Steam Workshop support for mods.
You can now play as a tribe in some scenarios.
Added torch lamp
Added pemmican for low-tech food preservation.
Research difficulty is now related to your faction's tech level. Researching techs above your level is harder. So if you're a tribe, researching spaceflight will be difficult.
Added research (needed for tribes only): complex clothing, electricity
Added research (needed for non-tribes only): pemmican
Added research: air conditioning, autodoors, gun turrets
Added 'ransom demand' incident. Can fire after one of your people is kidnapped.
Added "killed my X" social thoughts so people dislike their loved ones' killers
Added new class of "minor" mental breaks, which can happen at mood under 40%.
Added minor mental break: food binge.
Ground fertility is now reported on mouseover.
Added moisture pump, which slowly converts wet terrain to dry terrain. Requires power.
Hives now pop out glow pods - bug light sources that glow for 20 days (as long as they’re installed) and can be reinstalled or sold.
Added traits: creepy breathing, annoying voice. These are socially repellent.
Added trait: pyromaniac. Will go on firestarting sprees when stressed, and never puts out fire.
Added panther for jungle biome. Because I discovered panthers aren't real and I need to cope with this somehow.
There is now an orange glow to help you identify very hot areas.
Added/replaced animals created by the excellent Kay Fedewa[kayfedewa.deviantart.com]:
Caribou
Cassowary
Deer
Emu
Arctic fox
Fennec fox
Red fox
Gazelle
Husky
Ibex
Lynx
Megatherium (prehistoric giant ground sloth)
Ostrich
Raccoon
Rat
Turkey
Arctic wolf
Timber wolf

Interface
Added a row of colonist icons along the top of the screen, with various status info. They can be clicked to select, double-clicked to jump to, or box-selected to multi-select. These icons can be turned off.
Trading interface now lets you type in the number you want to trade instead of dragging to the number.
Animals tab now has gender and life stage informational columns
Animals tab now has a "slaughter" checkbox column to allow easy slaughtering of many animals
Animals tab now has checkbox columns for each trainable, to allow easy training of many animals
Reworked the right-click menu to be prettier, more readable, more solid, and better handle large lists of options.

Exploit solutions
Traders, visitors, raiders, kidnappers, animals, etc will now escape if surrounded by walls with no way out.
Manhunters and insects will attack doors if colonists try to hop in and out of them while getting shots off.
Hives must now be tended by insects, so if insects are all instantly killed by a turret wall, the hives will die out.
You can no longer avoid the 'executed prisoner' mood impact by just shooting or starving the prisoner; pawns will get a "prisoner died innocent" thought. A similar solution applies to the deaths of colonists.
Solved various powerleveling exploits. Once colonists have learned a certain (high) amount in a day, they'll learn at a much-reduced rate until the next day.
Flowers are no longer good animal feed (reduced nutrition).
Fixed exploit where players would give prisoner to raiders for kidnapping, to make raiders go away without a fight. Solution: Raiders only kidnap colonists.
Other
Updated to Unity 5.
World generation is now part of the new game process, instead of being separate.
Roofs must now be manually built and torn down by colonists; they do not appear and disappear instantly any more.
Reworked AI food selection algorithm to take into account personal mood impacts, rottenness, and other new factors. e.g. Now cannibals will actually seek out cannibal food because they get a mood bonus, while non-cannibals will avoid it.
Flow for opening worlds and savegames from old version is now improved; the "warning, old version" dialog comes before you open them instead of after.
Deworked mods config menu to have a much nicer selection and ordering interface.
Humans can now eat unbutchered corpses (though they really don't like it).
Infestations are easier and grow less exponentially.
Infestations only appear deeper underground now.
AI now runs away from grenades thrown by their own faction.
Tortoises aren't so deadly any more.
Animals no longer do incest.
Humans now do incest.
Seeds for world gen are now generated from actual words instead of random letter strings.
You can now set both minimum and maximum skill on a bill.
Beauty trait now has four stages: Staggeringly ugly, ugly, pretty, beautiful.
Some backstories now force pawns to have a given trait (e.g. Model->Beautiful)
Trade caravans can bring pack dromedaries.
Projectiles fired by hunting colonists no longer intercept random targets.
Some traders buy and sell furniture now.
Gut worms and muscle parasites vanish sooner.
Reworked ancient tomb loot generation. Plasteel is sometimes found on pod people. So are components.
Nuzzling is now a visualized, recorded social interaction.
Various refactorings to make modding easier and code easier to maintain and more flexible. Much more functionality is now implemented as composable ThingComps.
Many, many, many other balance changes, gameplay and interface refinements, and bugfixes.

Changelog Alpha 13

Changes in Alpha12b:
-Rebalanced animal hauling, traps, charge rifle, assault rifle.
-Rebalanced animal hunger rates and plant nutritions so animals need larger grass pastures to be sustainable.
-Thrumbo is much more powerful in combat.
-Sleeping pawns now wake up when harmed.
-Float menu column is wider to avoid cut-off text.
-Ship part incidents won’t occur so early.
-First raid comes a bit earlier on Cassandra and Phoebe.
-Fixed: Manual work priorities being used after switching to non-manual priorities.
-Fixed: Colonists have ‘colonist left unburied’ thoughts when tame animals were left unburied.
-Fixed: Eggs can only be used for simple meals
-Fixed: Trade items dropping in weird places.
-Fixed: Colonists incapable of violence can slaugher animals.
-Fixed: Alphabeavers leave the map after they sleep because they get hungry.
-Fixed: Date changes over at 6am, not midnight.
-Misc other fixes and improvements.
Change in Alpha12c:
-Poison ship part event now only drops one ship part instead of 2-3.
Change in Alpha12d
-Flashstorms are much less intense