Millennia is a very interesting and idiosyncratic game that has a lot more complexity under the hood than you'd initially expect.

On first pass its a Civ game with a relatively unique spin on the formula of alt-history strategy games, one that Humankind rode on quite heavily and Civ 7 is now making its own version of where-in you don't pick a civilization from some place and time in history and drag it through a series of somewhat-arbitrarily chosen eras from the stone age to the information age and maybe beyond regardless of how appropriate that is, a smash brothers of history and anthropology text-books playing all the greatest hits.

Rather you construct your civilization from the ground up, collecting a limited number of cultures and signifiers from across history from each era you pass into, while humankind left it at changing from one civilization to another as you cannonball through the cliffnotes of history Millennia takes it further on the alt-history spectrum and also varies up the ways that history can play out, having multiple potential eras that society can be guided or dragged into as long as requirements are met, some good, some bad, some fantastical. Indeed you can take humanity down some wonderfully whacky alternate paths.

Now these two things are obvious, they're the main selling points of the game on the steam page, where things actually get really interesting is what you actually DO in the game...
And much to my shock Millennia is actually something of a factory game.

Now obviously this is no Satisfactory or Factorio, neither in design or complexity, rather they've taken the various resources you can collect and produce in other strategy games like wool, copper, meat, logs, etc. and made a very interesting minigame out of it.

Instead of just plopping down a farm on top of a wheat resource tile and getting a flat food bonus to your city and calling it a day, to unlock the true potential of that wheat you need to run it though a production chain. First you harvest the wheat, gaining a minor but good to have bonus to food in the settlement, but you'll notice that you're not just getting a bonus to growth, that tile, when worked by a pop, is giving that city the wheat as an item, like a luxury or special resource in Civ 6, which is THEN conferring that food bonus to the city. And that's where it gets really interesting because you can then take that material and with another building (a mill in this case) and convert it into flour, gaining a marginally superior bonus, and then again, as you'd expect, with the construction of an oven that flour is transformed into its ultimate incarnation: BREAD. And just like that you've taken a simple grain that is good enough for a community getting on its feet to a monument of burgeoning human society everywhere, the mighty loaf.

Waffling aside the point is that throughout the entire game you're constantly playing this minigame in all of your non-vassal cities to take resources and turn them into more useful versions, and its not always a direct upgrade, a lot of the more advanced materials (like the numerous things paper (milled from logs) can be turned into) will take an item that produces one resource and turn it into something that produces another resource. And on top of THAT you're limited in every city by not only the amount of population that can work each tile but also the number of tiles that you have available to your cities, because nearly every step of the manufacturing processes requires a building that you physically place on the game map, taking up a tile that needs to be worked to function (most of the time) rather than being tucked away in the quantum realm that is the city centre.
This constant minigame of finding efficiencies and capacities is what makes Millennia truly incredible and fun to me, it also means that what resources and terrains you have available to you will directly influence how you choose which cultures (national spirits in the game) and which government types you choose, which feels SO naturalistic and true to life, cultures formed to best adapt to their environment and that's how it is in Millennia, its a brilliant keystone that makes the idea of this sort of rogue-lite civ-building-on-the-fly game work in a way that it kind of just doesn't in Humankind (at least to me) and its an extension on one of my favorite aspects of Civ 6 which is the districts system.

So in summary, the game has a deceptive amount of depth to it, a ton of replayability with a bunch of national spirits and eras to mix and match and is nice to look at to boot.

Millennia is a very interesting and idiosyncratic game that has a lot more complexity under the hood than you'd initially expect. On first pass its a Civ game with a relatively unique spin on the formula of alt-history strategy games, one that Humankind rode on quite heavily and Civ 7 is now making its own version of where-in you don't pick a civilization from some place and time in history and drag it through a series of somewhat-arbitrarily chosen eras from the stone age to the information age and maybe beyond regardless of how appropriate that is, a smash brothers of history and anthropology text-books playing all the greatest hits. Rather you construct your civilization from the ground up, collecting a limited number of cultures and signifiers from across history from each era you pass into, while humankind left it at changing from one civilization to another as you cannonball through the cliffnotes of history Millennia takes it further on the alt-history spectrum and also varies up the ways that history can play out, having multiple potential eras that society can be guided or dragged into as long as requirements are met, some good, some bad, some fantastical. Indeed you can take humanity down some wonderfully whacky alternate paths. Now these two things are obvious, they're the main selling points of the game on the steam page, where things actually get really interesting is what you actually DO in the game... And much to my shock Millennia is actually something of a factory game. Now obviously this is no Satisfactory or Factorio, neither in design or complexity, rather they've taken the various resources you can collect and produce in other strategy games like wool, copper, meat, logs, etc. and made a very interesting minigame out of it. Instead of just plopping down a farm on top of a wheat resource tile and getting a flat food bonus to your city and calling it a day, to unlock the true potential of that wheat you need to run it though a production chain. First you harvest the wheat, gaining a minor but good to have bonus to food in the settlement, but you'll notice that you're not just getting a bonus to growth, that tile, when worked by a pop, is giving that city the wheat as an item, like a luxury or special resource in Civ 6, which is THEN conferring that food bonus to the city. And that's where it gets really interesting because you can then take that material and with another building (a mill in this case) and convert it into flour, gaining a marginally superior bonus, and then again, as you'd expect, with the construction of an oven that flour is transformed into its ultimate incarnation: BREAD. And just like that you've taken a simple grain that is good enough for a community getting on its feet to a monument of burgeoning human society everywhere, the mighty loaf. Waffling aside the point is that throughout the entire game you're constantly playing this minigame in all of your non-vassal cities to take resources and turn them into more useful versions, and its not always a direct upgrade, a lot of the more advanced materials (like the numerous things paper (milled from logs) can be turned into) will take an item that produces one resource and turn it into something that produces another resource. And on top of THAT you're limited in every city by not only the amount of population that can work each tile but also the number of tiles that you have available to your cities, because nearly every step of the manufacturing processes requires a building that you physically place on the game map, taking up a tile that needs to be worked to function (most of the time) rather than being tucked away in the quantum realm that is the city centre. This constant minigame of finding efficiencies and capacities is what makes Millennia truly incredible and fun to me, it also means that what resources and terrains you have available to you will directly influence how you choose which cultures (national spirits in the game) and which government types you choose, which feels SO naturalistic and true to life, cultures formed to best adapt to their environment and that's how it is in Millennia, its a brilliant keystone that makes the idea of this sort of rogue-lite civ-building-on-the-fly game work in a way that it kind of just doesn't in Humankind (at least to me) and its an extension on one of my favorite aspects of Civ 6 which is the districts system. So in summary, the game has a deceptive amount of depth to it, a ton of replayability with a bunch of national spirits and eras to mix and match and is nice to look at to boot.