This mod is no longer being updated. No further work will be done.

This mod is all about the details. You will not see any huge changes that completely changes how the game is played. However, there are a lot of minor alterations to pretty much every aspect of StarCraft 2, including scale, weapons, units, projectiles, tech, audio and visuals.

The 12 mission custom campaign Scattered is based on this mod.

Main purposes:

Make the game slightly less frantic by reducing the maximum income rate and making battles last slightly longer.
Create the illusion of bigger maps and somewhat more sensible unit scaling.
Tweak visuals and sound for an even more engaging combat experience.

While I started out keeping a complete history of every change I made this proved to be too time consuming, and the list grew to the point where no one would ever want to read it. So below I'll try to present as much as I can remember from the top of my head.

Place the file Tranquility.SC2Mod in your StarCraftII/Mods folder.

Terrans Protoss Zerg

In short

The baseline scale of all units (not structures) have been reduced by 30%, creating an illusion of larger maps.
The baseline speed of all units have been reduced by 30% to match the scale change. Most aircraft, however, are slightly larger and faster.
The baseline firing ranges are unchanged, but the smaller units effectively make them longer. Melee units have been buffed slightly because of this.
The baseline training time of all units have been increased by about 20%.
The baseline damage per second of all units and structures have been reduced by 30%, making battles last slightly longer.
Infantry-ish units (marines, marauders, zerglings, hydralisks, zealots etc.) are smaller, weaker and cheaper.
The income rate have been reduced slightly. The cheaper low-tier units makes up for this in the early game, but higher tier units are harder to mass produce.
EMP, psi storm and fungal growth are less effective against high-tier units.
All structures except planetary fortresses, bunkers, supply depots, photon cannons, pylons, spine crawlers and spore crawlers have had their hitpoints doubled.
Many protoss units have swapped shield and armor stats. That is, if a unit had 20 life with 1 armor and 10 shield with 0 shield armor, it now has 10 life with 0 armor and 20 shield with 1 shield armor. Note that the EMP is nerfed, so this is not necessarily a bad thing.
Battlecruisers (now called cruisers) and carriers are significantly larger, slower and more powerful than before, but also very costly and time consuming to manufacture.
A few new units and research options (no custom models, so don't expect anything too fancy), also firebats, medics, vultures, diamondbacks and scouts are now buildable. Medics, firebats and diamondbacks have been nerfed.
There are also a lot of cosmetic changes including (but not limited to) reworked muzzle flashes, firing sounds, projectiles, impact effects, impact sounds, tuned sound volume for individual effects, smoother acceleration, deceleration and turning animations for large units, e.g. a large tank will no longer swing around in a split second, and will not stop on a dime.
Some units, most notably hero units and some merc units, aren't done yet. It's on my todo list and may come in the future. For the moment only the siege trooper (former war-pig) and spartan are more or less complete.
The "hardened shield"-effect is now the "hurts as hell"-effect and is present on several protoss units. It does not reduce any damage but is merely an indication that the shield has taken a very heavy hit.

Details

Protoss

Probe: Mostly unchanged.
Zealot: Weaker, cheaper, smaller.
Stalker: Mostly unchanged, smoother movement.
Sentry: Mostly unchanged, new weapon.
High templar: Smaller, psi storm damage reduced.
Dark templar: Mostly unchanged, smaller.
Immortal: New weapon visuals, faster fire rate, DPS unchanged, range increased, hardened shield removed, stronger shields, weaker armor.
Colossus: Hitpoints increased, DPS increased, cost increased.
Archon: Mostly unchanged, smaller.
Observer: Mostly unchanged.
Warp prism: Stronger shields, weaker armor. Larger.
Phoenix: Stronger shields, weaker armor. Larger.
Void ray: Speed reduced, speed upgrade available. Hitpoints increased, DPS increased, cost increased.
Carrier: Everything is heavily buffed. It is large, slow, very powerful and very expensive. Has a yamato shield upgrade that greatly reduces incoming damage from yamato cannons.
Mothership: Hitpoints increased, DPS increased, cost increased.
Scout: Photon blasters reworked. AG and AA photon blasters, no missiles. Speed upgrade agailable.
Elancer: New artillery unit. Range upgrade available. Upgraded it will reach almost as far as a siege tank. Does not have to deploy. Does no splash damage. Slow moving.

Terran

SCV: Mostly unchanged.
Marine: Weaker, cheaper, smaller.
Marauder: Much weaker, cheaper, smaller.
Reaper: Mostly unchanged. Smaller.
Ghost: New weapon visuals. Smaller.
Hellion: Mostly unchanged.
Siege tank (tank mode): Slightly stronger, more expensive. Fire rate greatly reduced, DPS unchanged. Reworked weapon.
Siege tank (siege mode): Range increased, DPS reduced, armor bonus removed, weapon hit delay added, larger muzzle flash.
Thor: Smaller, slower. Projectile weapons, tweaked firing sound, larger muzzle flashes.
Viking: Mostly unchanged.
Medivac: Mostly unchanged.
Raven: Auto-turret is permanent, costs minerals and gas in addition to energy and has a reworked weapon. Point defense drone nerfed due to many units having slow-firing projectile weapons.
Banshee: Mostly unchanged.
Cruiser: Replaces battlecruiser. Is significantly larger, more powerful and more expensive than the old battlecruiser. AA lasers can fire on the move in any direction and has increased range.
Firebat: Weaker, cheaper, smaller. New weapon visuals. Damage bonus against biological, damage reduced against everything else.
Medic: Significantly reduced healing rate. Smaller.
Vulture: Slightly reworked weapon. Replenishable magazines upgrade available.
Goliath: Now comes with true auto-cannons, a personal favorite.
Diamondback: Can no longer fire on the move. New weapon visuals, increased range, reduced dps.
Wraith: Cloaking ability tied to basic cloak research. Missiles removed, now uses AA lasers.
Claymore tank: New dedicated anti-armor unit. Large and cumbersome, but with a long range, high damage, slow firing cannon. Will take down a thor in one-on-one combat, but is less useful against small, unarmored targets, and has no air defence.
IFS tank: Infantry Fire Support tank. New artillery unit. Essentially a smaller, less powerful siege tank that doesn't do any splash damage.

Zerg

Drone: Mostly unchanged.
Queen: Mostly unchanged.
Zergling: Weaker, smaller, cheaper. Health upgrade available.
Baneling: Mostly unchanged.
Roach: New weapon visuals. Range reduced. No change to hitpoints or dps. However, due to the reduced efficiency of infantry such as marines, zealots and most notably marauders, roaches can be a bit more dangerous than one might expect.
Hydralisk: Weaker, smaller, cheaper. Health increased (proportionally). Health upgrade available.
Infestor: Smaller. Infested terran throw range reduced. Infested terran duration and energy cost greatly increased.
Ultralisk: Hitpoints, DPS and cost increased. Slightly more cumbersome.
Overlord: Mostly unchanged.
Overseer: Mostly unchanged.
Mutalisk: Mostly unchanged. New weapon visuals.
Corruptor: Mostly unchanged.
Brood lord: Broodling duration increased, broodling spawn rate greatly reduced. Additional weapon added. The broodlings can be killed off quite easily, but the brood lord will still do damage with the weapon. If the broodlings are not killed off, the DPS of the brood lord is higher than vanilla, otherwise slightly lower.

Known bugs

Some upgrade model changes aren't working (zergling, roach) and thus will not change apperance when upgraded. Because of this, zerglings now always have wings.

Tranquility Mod