WHOA!
This is definitely not more of the same!
I've only been messing around with it for about an hour and I don't know what's going on yet, but I think that we're definitely in for a much better game than the last.
1) Those who felt the last one was too simple, take heart, you need to RTFM to play this one.
2) Fleet management is overhauled entirely. You now have a series of admirals, each with with differing stats, who head up fleets. In order to create a new fleet, you must have a command ship ready for the admiral waiting in reserve. You do not directly order groups of ships in the manner you did in the first game. Instead, you select systems/targets and designate missions to fleet admirals. The admirals tell you how long it's going to take to complete the mission, and in some cases it will even cost money.
3) Space stations are a lot more sophisticated and broken down into several groups. For example, in order to facilitate interspecies trade, you must build space stations and outfit them with modules to accommodate other species.
4) In addition to weapon hardpoints on ships, you can assign modules which change the nature of the ship altogether. Examples being, marines(which increase resistance to boarding by providing combat ready troops), psionic warfare teams, logistics teams, auxillary power, engineer corps, etc.
5) Colonization is no longer a manner of churning up a bunch of ships and watching them disappear when you colonize a planet. Now colonization fleets(often comprising of construction/colonization/mining ships) will make round trips with supplies and population until the planet you are trying to colonize is developed.
6) Oh yeah, there are now multiple planets per star system, and differing types of planets(e.g. gas giants, solid planets, etc).
Oh and while destroyers are no longer in the game, there are both drones and 'battleriders' which are essentially destroyer class ships w/o interstellar drives that deploy similar to fighters.
It's pretty fucking different is all I know to say.
Have experienced some bugs with the sound cutting out until I restart the program though.
