XTA (eXtended Total Annihilation) was originally a mod of TA:CC patch 3.1, which then has continued in the Spring engine. It is in principle very similar to TA:CC, but there are some differences, not notably the fact that Moho Mines take 300 energy to run.
The folowing is taken from http://springrts.com/wiki/Ota2xta
Basic xta description for ota players
All level 1 units are worth building:
- Stumpies and Hammers are decent anti*MT choices.
- Jeffies are very dangerous, but they do cost nearly 200 metal.
- There is a level 1 gunship now.
- Freedom Fighters and Avengers have been given their sorely needed boost.
All level 2 units are worth building:
- Sumos have tons of armor, huge range, rapid fire rate and move at medium speed.
- Their 2.1k metal cost is well worth the unit you get in exchange.
- Goliaths are horrifying weapons: 23k armor (66% as much as an OTA Krogoth), missile*alike range, BB*class shell.
- But they don't quite come for free: 2.8k metal.
- Mavericks build much faster.
- Flakkers fire at ground targets, and their antiair potential has been improved.
- Warlords and Leviathans were massively boosted in terms of armor and firepower.
- Krogoths are totally krazy, man.
Nearly all defenses were revamped:
- MTs are nearly unchanged, except they are smaller so that you can fit more of them into the same space.
- LLTs have the range and power to be worth building.
- HLTs are a bit costly, but they can reach further than missiles.
- An excellent early creep weapon.
- Ambusher/Toaster are now buidable by level 1 Construction units and fulfill the same role as Guardian/Punisher in OTA.
- Guardian/Punisher are level 2 structures with much longer range, firepower and armor.
- Annihilators and Doomsday Machines have far higher range, more armor, and they don't blow up half your base when they die.
- With all the armor available in level 2 units, you will need them.
- BB has lost some accuracy, Intim lost some range. Both lost firepower but gained armor and area of effect.
- EMP/Neutron silos are short ranged, very fast building budget nukes.
- Antinuke silos build their missiles faster to accomodate for EMP/Neutron change.
Resource structures have changed less than other parts of the mod but the gameplay impact is very big:
- Metal Extractors self destruct instantly and without damaging anything around them.
- This makes upgrading to Moho Extractors less tedious.
- ARM has a Mobile Fusion, CORE has a stationary Light Fusion.
- Both cost 1500 metal and make about 300 energy: ideal to fuel your Moho economy.
- Moho Extractors are quite cheap (750 metal) and make lots of metal, but they drain 300 energy.
- You want to have at least a Geo or Mobile/Light Fusion before you build a Moho.
Cloakable Fusions have taken the place of OTA's regular ones.
- Regular Fusions now cost 10k metal. Their armor and energy production have been increased appropriately.
- This reduces the need for Fusion farms in very late game.
- Mine layers have several types of mines that are worth building and move faster.
- Energy and Metal Storage stores a lot more.
- Missile frigates have got firepower and hitpoints suitable for their cost.
- Mobile artillery and lugers are not inaccurate.
- Decoy commanders build as fast as real commanders.
- The build range on all con units has been increased.