Quick Questions

1) Destroying the enemy is the only win condition. However, there is a surrender option that the AI does use at various degrees of hopelessness and it doesn't give much notification, so it's possible to win and still have enemy colonies in the game.

2) There are three things about culture you need to know.

First, culture output stacks for every broadcast station and is split evenly among the phase lanes leading out from a planet. Because it stacks, there are many times when one building is not enough. If you're generating 5 culture/sec (you can hover over the planet and it will show you in its infocard) and the enemy is generating 10, his is going to win and take over your planet. So if you see your culture being pushed back, build more broadcast centers quickly.

Second, planets under the effects of culture have modified allegiance. Planets under friendly culture have +10% max allegiance (so 10% more credits and resources generated). The Advent have a tech in the late civic tree that gives them another +10%, which means under culture the minimum allegiance is 55%, with 45% for the other races. Under hostile culture, allegiance steadily decreases until it reaches 0, at which point the planet rebels and goes neutral. This is what happened to you. To see the allegiance loss/gain, select the planet in question and then look at the bottom of the screen - to the left of the planet image in the center are 3 fields, one of which will show your current allegiance and if you hover over it you'll get an info window with the rate of change. This rate of change is capped, so if the enemy overtakes your culture by 10/s or 40/s, it's going to decrease at the same rate. (caveat: if the difference in culture is very small, it may decrease slower than the max rate, it does depend on the culture difference, but this doesn't happen too often).

Third, each race gets ship bonuses in friendly culture as part of their culture research line in the civic tree. TEC get faster antimatter regeneration, Vasari get bonus damage, and Advent get bonus shield mitigation (the Advent's superweapon that fires a culture shell also gives them a damage bonus, but normal culture does not).

3) Culture output decreases with every jump, but usually a single center is enough to go about 2 jumps (so affects 3 planets) before it starts spreading too slowly. There is no hard cap. The more buildings you have on a planet, the farther it can go before it starts going too slow. So if you're only outputting 6, it'll go to 3 after one jump, 1.5, then .75 and so on. If you're outputting 30, it'll go 15, 7.5, 3.75, 1.375 - so it can spread farther.

Because of that, there's no set rule on how many to build and where, just play it by ear. If it's going too slow, build some more in that area.

Hope this helps a bit

1. atm, the only real way to win the game is to destroy all of the enemies planets, or destroy enough to make him surrender (depending on if you are playing entrenchment or not) as it stands, AI in entrenchment tend to surrender more than in the original version. However, with the new x-pack being developed, there will be new and different ways to win the game, i assume via culture, economy, and sabotage etc, at least

2. so, culture is spread by broadcast centers (each race is called something different but meh). the more you have at a certain planet the faster culture spreads/the slower it retreats (if at all). however, there are researchable upgrades that improve the effeciency/speed of culture spread and reduce culture loss. each race has different upgrades. The Advent are culture masters, so if you were playing against them, you would have to have a decently strong culture to resist. Other factors that affect culture are any Capital ships and or Starbases in orbit. these slow enemy culture from approaching your planets, and help speed up culture loss at enemies planets with no culture centers.

The way it works is there is an allegiance value attached to all your planets. this value is affected based on: how far that planet is from your homeworld, whether it is connected with trade ports or not and friendly and enemy culture spread (i think i got them all, im not sure) the further a planet is from your homeworld, the easier it is to be lost to enemy culture, as the max allegiance value is already much lower than normal, so make sure you have a broadcast center at or close to your border worlds. a planet is lost to enemy culture when your allegiance on that planet reaches 0. the planet then becomes neutral. i think thats all you need to know about planet loss and culture... ask if you are still unsure

3. culture will spread to other worlds at a speed depending on research done and how many broadcast centers are nearby. you dont need to build it on every world, but on/close to your homeworld, and on/close to every frontline planet is a very wise strategy, as well as a few in the center of your empire.

think of it like this. you want to fill an ice cube maker with water, but your tap is broken and only lets out a trickle of water. if you use one tap, each cube thingy will fill up with water slowly until it overflows into another cube thingy. but, if you want to fill the ice cube maker as fast and as completely as possible, optimally, you would get between 3 and 6 taps to trickle water into each corner of the ice cube maker, as well as in the middle. this fills up the ice cube maker much faster, and much more completely than with the 1 or 2 taps. its not a perfect analogy, but its roughly correct.

about spammable structures, youd be better off spamming trade ports first, and refineries second, personally, i place trade ports along the most optimal route, and a few other planets, and refineries at ice/volcanic worlds and worlds next to UCGW (UnColonisable Gravity Wells) with neutral extractors in them (its like a resource asteroid you find at your normal planets, but located in a gravity well like a debris field or plasma cloud etc

hope that answered your questions

You win when you defeat all enemy planets.

The reason is that they have more broadcast centers than you and as such, they are able to overwhelm yours.

And yes... I am assuming that you are playing as the TEC, so I recommend spamming the trading post as doing so (combined with the cheapo upgrade in the civilian tree) will give you almost unlimited credits...

Excellent. Thank you very much for the clear and concise answers.