Kingdoms and Castles isn't the most challenging or complex city-building game I've ever seen, but it is one of the best to just pick up and start playing.
The game -- released on PC earlier this week -- randomly generates a small patch of land for you, then asks you to build a lil' Medieval settlement on it. You're given a few settlers and resources to get going, but after that you're on your own. Food, shelter, stone, iron, bread, soldiers, churches, you need to grow, hire or build everything else from there.
To stop the player from just going nuts and building everything at once, K&C puts a cap on your progress by using your settlement's population as an energy meter. The more people you can attract, the more buildings you'll be able to "power" and thus gain resources from, the more stuff you'll be able to do. If people leave, or die, then essential services will go unserved, and you might find yourself in trouble.
There is definitely trouble at certain points in K&C anyway, because to keep players on their toes the game likes to throw crisis events like plagues, dragons and viking invasions your way. Each of these can be countered fairly easily, but they're enough of a threat to always have you wondering whether to spend workers/resources on a new church that you definitely need now, or on better defences for your town which you may need more, but at some random point down the line.
And that's about it. There's no story or endgame to work towards, just the satisfaction of seeing a small little village grow into a medieval city. K&C has definitely traded depth for accessibility, with not much asked of the player aside from placing buildings and roads, and while that will disappoint some (the inability to be able to manually assign workers to specific jobs is a bit of a pain), I kinda liked it: I found that I was hooked on the building process after only a few minutes of playtime, and I've since played through three separate games since each reroll of the terrain can present new challenges and ideas for your build.
Bread. Everyone always wants more bread. Can't get enough of that bread.
The only things you have to manage outside of the building are preparing for winter (you need to have food stored), some very streamlined citizen happiness (they hate smog and living in slums, love churches and libraries) and some basic taxation and military commands (which involve sending an army to fight vikings and/or building defence towers to counter incursions). They're rare diversions, though; you spend most of your hours in K&C wondering which part of your cute little town you're going to put a cute little bakery in next.
You can raise a small, simple army to go and fight the vikings.
Kingdoms & Castles isn't a brutal survival game, nor is it a detailed and accurate simulation of Western European settlement construction in the late Medieval era. It's intended as a game about having fun building a cute little village, and that's exactly what it delivers.