Addictive as hell, but not without it's problems
Alpha Centauri is a sequel to Civilizations II, like it's predecessor it's a round based world building game, but instead of focusing on earth, the game moves the setting to a planet in the Alpha Centauri system, where after an reactor failure and crash landing different competing factions try to colonize the planet.
On the technical side the game stays very close to Civilizations II. The game is presented in an isometric perspective and the worldmap is the regular grid based rectangle. Some enhancements do exist, such that the unit icons are now in 3D and rotate when you drive around with them and the map now has height, like games like Populous. The map is also zoomable, but I didn't found that much helpful, as the units become to hard to identify. Overall all those changes seem rather superficial. One problem with the game is that it no longer runs in a window, but in a 800x600 fullscreen mode, thus you can't increase the viewable area to fit modern screen resolutions.
On the gameplay side it also follows into Civilizations II footsteps. You have builder units that can build roads or enhance the cities surrounding. You can create new cities, have diplomacy and a bunch of units to make war against other nations. Research for technologies gives you new abilities over the course of the game. Movement in Alpha Centauri is unlike in other round based strategy games very slow, a lot of unit types can only move one square each turn. This probably a large part of it's addictiveness of the game, as while it units it makes the game itself quite fast paced, decisions on what to do with a unit are simply and quickly done and then you instantly jump to the next unit and so on. There is not much space in the game for just pondering on what to do next, there is always something that needs to be done and the game does a good job of jumping you right to that spot.
The user interface is probably my biggest issue with the game. While the graphics do look ok on screenshots, they are incredible hard to read when you actually play the game. Unit types are hard to distinguish from each other, with flying units it's hard to pin point on which square they currently stand and in general there is just far to much visual noise in the image, especially later in the game when you have upgraded terrain, roads and units all over the place it just gets hard to figure out what exactly the current situation is. On top of that the game also hides information, units for example are stackable, multiple ones can be on the same square, but you don't see that until you actually select that specific square, on the map all you see is a single unit, the rest are invisible. Getting to now the strength of an enemy unit also is cumbersome, as again, the game doesn't just display it when needed, but only when you select the unit manually with the cursor. The cursor mode itself also has to be first enabled with a button press.
On top of those presentation issues the game also suffers from an obtuse control scheme. All unit commands are placed in an annoying little submenu, they don't just pop up as buttons when the unit is selected, instead you have to navigate a to that submenu to reach them. This makes it extremely hard to find what you are looking for or even just knowing that this or that function exist in the first place. Each command does come with a keyboard shortcut and once you learn those the game plays smoothly enough, but learning them certainly takes quite a bit of time and more then a few times you will wonder in which submenu some function is hiding.
The strategy in this game also seems to fall a bit short. While the city building and expansion is certainly fun, trying to do a larger scale war just gets tedious. Units movement and building is extremely slow and thus bringing the needed units to the location where they are needed can take quite a long while, especially when you try to do an attack where you have water in between. This caused me to never much bother with properly micro managing the units I send, instead I just took whatever I had at hand and threw it at the enemy. This worked for me due to playing on a lower difficulty, but I wouldn't recommend trying that on the higher ones. There are some potential things hidden in the interface such as auto-forward routes to make unit movement a little more automatic, but the game doesn't make it exactly easy to find those features and I am rather sure that I might have overlooked a few ways the game allows to automate things.
Where the game shines is in it's science fiction aspects, while it doesn't come with any kind of big story aside from the intro, exploring the tech tree and watching the descriptions and videos is certainly fun and the game has a lot of that. The game is also quite up to date with it's fiction and throws terms like the Singularity around that only entered mainstream pop culture a decade later.
I am probably not the best person to judge a game like this, as I normally stay away from round based strategy and haven't really dug that deep into the mechanics, but overall I certainly had quite a bit of fun with the game. The interface issue are annoying, but by using the keyboard shortcuts one can overcome them. Most of them also turn out to not be that big of a deal, as the game will automate a lot of the work, it will jump you to units that haven't moved this round, warn you when you might have forgotten a unit, even give advise when you throw a far to weak unit against a strong one. The game also autosaves every turn and provides multiple levels of autosaves, so that even when something goes fundamentally wrong, there is always a way to undo do it if needed.
The Alpha Centauri: Crossfire expansion adds two new alien factions and some new human factions, while those do mix the game up a bit, they don't change it in any fundamental way.
A game of Alpha Centauri on the large map on Specialist difficulty takes around 8-12 hours, depending on what ending you try to achieve. The small map can be done in around 3 hours. I played in total for around 26 hours.