How do you start developing a new project?

Question

Mobile development

Actually interested in how you build the architecture of the application, roughly speaking the sequence of actions.
For example:
1) Brainstorm
2) Evaluation and sifting of everything received (I wonder how exactly you sifted? Just throw it away or put it somewhere to the side?)
2) "Sort" the result of the brainstorm
3) Drawing up an "N" diagram,
etc.
Of course, it is not necessary to follow my example - you can use the usual story.
Why am I interested in this?
I am developing a mobile application (medium complexity 2d game) as part of my thesis at the university.
But please understand me correctly, I will use this information not only in the diploma, but also in the development of my future projects.