How is difficulty increasing in games designed?

Question

Game development

Hello.
The question has long been of interest - how does the difficulty iterate in the game from level to level, so that the new one being created is a little more difficult than the previous one? Is it manually tested or are there automations?
The question is closer to the abstract, so the answer is suitable for any example - at least unity, at least pygame.
I would be grateful for links to read.
Thank you.

Answer 1

There is such a position - a game designer. Which calculates the complexity of the levels in a table and enters it into the balance of the game - that is, into the configuration files. There can be no examples here - neither the unity nor the pygame have anything to do with it - it's just a matter of configs.
Google "game design difficulty curve".