Reus is probably my favorite god-game of the past decade.
At its core, the game is something of a 2D (or really, technically 1D) Sim City RTS. You cannot directly control humanity, but you create and arrange resources in order to help them thrive. Villages need Food, Wealth, and Tech, which can be gained in various combinations from Animal, Plant, and Mineral resources.
It may not be obvious from the screenshots, but the planet is divided up into individual tiles. Each tile can only be occupied by one resource or building at a time, though you can usually "overwrite" a tile's contents.
You direct your four giants (Ocean, Rock, Forest, Swamp) to terraform the world's surface and to place resources on specific tiles. Eventually humans will settle near a resource, reserving several contiguous tiles as a town square, and setting up borders a certain distance from the square. As a village develops, the borders will be pushed back, opening up additional tiles for the village to use.
Most of the game's progression is context-sensitive.
Giants have vague powers, such as "Create Exotic Animal," but the TYPE of animal is determined by which biome (Forest, Swamp, Desert, Mountain, Ocean) the power is cast upon.
Individual resources may grant bonuses depending on what occupies the adjacent tiles (Salt is more useful if there is a different mineral right next to it).
Giants are able to upgrade the attributes of certain resources. For example, the Swamp Giant is able to increase the amount of Tech provided by any plant tile. Improving aspects in this way unlocks the ability to upgrade the resource to a more valuable/effective (but often more specialized) resource. By manipulating aspects, you can develop Blueberries into either Strawberries or an Apple Tree. Each of those choices also has branching upgrades with different bonuses. In order to keep the choices from getting overwhelming, certain upgrades must be unlocked with achievements.
There are two separate classifications of animals, two of minerals, and two of plants. With all the valid combinations of resource-types and biomes, there are 25 possible entry-level resources, each with various upgrade paths.
A village's "type" is determined by whether the town square is planted on Forest, Swamp, or Desert tiles. This will determine what sort of civic projects the villagers will want to build (Forest emphasizes agriculture, Desert emphasizes wealth, and Swamp emphasizes technology).
Villages will occasionally decide to construct specialty buildings. In order to successfully complete these projects, the village must reach a certain quota of Food, Wealth, and Tech (or other factors) within a predetermined length of time. It's worth it to help villages reach these goals, because they unlock achievements and award you a village ambassador. Each ambassador can be assigned to one of your giants, who will as a result unlock (or strengthen) a creation or aspect power. The type of power affected is determined by what type of village provided the ambassador.
Each village has a Greed meter. When a village acquires resources too rapidly, the Greed meter will fill, encouraging that village to attack neighbors (or the giants!). This is disruptive to your ability to efficiently and effectively develop these communities within the time limit (Once time runs out, your accomplishments are judged and you are allowed to continue playing, but some achievements must be reached while the clock is still ticking).
The real meat of this game comes from trying to shuffle your resources around within a village's borders in order to maximize context-specific bonuses, because the project the village wants to build just requires SO MUCH of a given resource (or several!) that it needs to be your singular goal. Except it's your multiple goal, because your other villages are also trying to build their own projects, and you can't upgrade this mineral over here until that giant walks over there and casts that aspect upgrade on it (Did I mention the giants have to walk to the tiles where you want them to take action? They're not fast). Since different projects have different dependencies, it's often necessary to maintain at least one of each type of village (Forest, Desert, and Swamp) to ensure a variety of ambassadors (and, by extension, upgrades).
Reus has vibrant art assets and a pleasant soundtrack. The game is fairly easy to pick up but the depth of it might catch you off-guard. You can also choose from a variety of modifiers (such as planet's size or a speed boost for your giants) when starting a new game. Some of these modifiers prevent you from unlocking high-level achievements, but they are a nice way to get a head start in what can easily turn into a several-hour session.
If you like Populous, Sim City, or Black & White, I would recommend giving this game a try.