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When you hack something, it uses up HaP (hacking points), a valuable resource that can only be increased by increasing the AIP. Having low/negative AIP doesn't prevent you from hacking, but it causes the hacking response to skyrocket to a level that's pretty much impossible to deal with. In addition, the AI's hacking response gets exponentially more fearsome the more times you hack, even with equal AIP. Combine that with the fact that later hack attempts usually occur at higher AIP, and the AI hacking response can get
really nasty, so much so that on high AIP games it's not unusual to have unused HaP, simply because the AI would send a game-ending response if you tried anything. There will always be far more hackable objects than what you'll actually be able to hack, so it's best to save your HaP until you've scouted a fair portion of the map, or if you come across something particularly useful/annoying.
How desirable it is to take a planet with relatively little strategic value varies greatly depending on how long the game has been going on, what difficulty you're playing on, how many planets there are, what the map is shaped like, what factions you have enabled, and how you want to win the game. And each of these affects the relative importance of the others, so the only way to really know is through bitter experience - though I'll try to put down a condensed version.
Over everything else, how you want to win determines most of the other variables. How you want to win the game can generally be broken down into high AIP and low AIP. On high difficulties, winning with high AIP is pretty much impossible (at least that's my understanding, I've never played above 7/7 (Yet!)). A high AIP route usually involves having minor factions enabled that can boost your power but require lots of resources (zenith trader, golems, spirecraft, fallen spire, etc), and having map types with chokepoints (clusters, x type, tree, snake, etc). The minor factions are important because a linear increase in AIP does not equal a linear increase in difficulty - going from 200 to 300 is not as difficult as going from 300 to 400; as a result, a high AIP route means you either need to be a better player, or have some fun toys to give you an edge. The map types are important because more territory generally means more avenues of attack for the AI. In that case, taking planets with nothing on them could actually be really beneficial - stopping a planet with connections to 4 of your planets from sending waves or filling with AI units can easily be worth the 20 extra AIP. Plus, the more planets you have far away from the frontlines, the larger the economy you can support. However, with really interconnected map types, you may have to take a LOT of territory before you can really cut down the AI attack vectors and create safe (but fragile) economic planets far away from the fighting. While you try to take all that territory, you'll have increasing AIP, MORE AI attack vectors, and a stagnant economy - a recipe for disaster. So unless you're glutton for punishment (though I guess if you weren't you wouldn't be playing AI War in the first place
) High AIP should really only be done for map types with few connections, or ones broken into chunks that you can conquer relatively quickly.
Whew, I think I'm all typed out for now. Anyone else is welcome to add to that, or answer Worblehat's other questions. If not, I'll try to get to them tomorrow.
Ninja'd by Keith, the original ninja.