Spore

Spore is a simulation game made by Maxis and Will Wright. Released in 2008, the game is about evolution and in the game you advance to several stages including the Cell Stage, Creature Stage, Tribal Stage, Civilisation Stage and Space Stage.

Spore in fiction.
This is a spore fandom website but the main fiction is on SporeWiki

Cell Stage
The Cell Stage is about the growth of the player's creature cell. The player can choose to be a herbivore or carnivore. You have to eat food to grow your cell.

In this stage, the player guides a cell of his or her new species through a 2.5D primordial ooze consisting of other cells, plants, bubbles, debris, various food particles, leftover bits of killed cells, and crystalline structures. The player's cell can eat smaller cells (if the cell is carnivorous or omnivorous) or leftover bits of food in order to evolve to a being of higher understanding. The player's organism can be attacked and eaten by organisms of larger or similar size (even smaller ones can damage and kill it). The main goal of this stage is to develop a brain and become large and strong enough to move onto land and begin the Creature Stage. In this stage, the only species besides the player's own are Maxis creations.

The Cell Stage also serves as a sort of tutorial for the later stages, introducing the basic tools of the fixed camera mode where game play mainly consists of eating and evolving by adding parts to the cell. The view becomes largely compressed if the cell does not have any sight; in other words, the outer area of the screen becomes black and fades away as it gets closer to the middle. This also happens in the Creature Stage.

As you progress, you get both bigger and less transparent (if you have high graphical settings active). After you grow and zoom out, peer-size cells are now prey size and stop spawning. At the same time, even larger creatures from the background will enter the playing field and try to eat you.

Upon filling the progress bar, a cut scene will play detailing the player's avatar developing a small brain-like organ; at this point, the player will be allowed to progress to the next stage, where they would be rewarded a Trait card for their efforts, this trait card will then determine the species diet for the rest of the game, the player can then progress onto the Early Creature Creator.

Creature Stage
The second stage in Spore.

The core mechanic of the Creature Stage is to gain DNA points by befriending or hunting other species, with the goal to increase the brain size of the player's creature. The Creature Stage ends when the creature reaches sapience and the player chooses to move on. The player has the ability to unlock creature parts that are useful for hunting or socialization; most creature parts have abilities useful to these strategies, and in addition, the creature has one consequence ability gained by the player's strategy in the Cell Stage. Each increase in brain size will gain one space to add a member to the player's pack (including befriended creatures). There is a maximum of three spaces. The creatures in the player's pack can make it easier to befriend or attack other creatures. The player can use this as part of a long-term goal for determining the consequence abilities in future stages, based on hunting or befriending other species, or a balance between the two.

At some stage, the player's species will migrate to another part of the continent; reuniting with them is another way to gain DNA points.

After gaining a certain amount of DNA your creature's brain will increase in size. After the first increase in size, you can use social skills to persuade other creatures to join your pack. The maximum amount of creatures you can have in your pack increases by 1 each time your brain increases, near the end of the stage you can have 4 creatures in your pack (including yourself). After a creature's brain becomes big enough and they become sapient, the player can enter the Tribal Stage.

Also, as your creature's brain gets bigger, their maximum health level will increase, allowing them to survive fights against tougher creatures. They also appear to grow larger.

Each time you get closer to the end of Creature Stage different animals become stronger and have more to kill.