I have done something similar - building a game while working full-time. But my approach was the complete opposite of this article.
No real process, no plan, no scrum method, not even a trello board to track progress and todos. Personally, I enjoyed the "fun" of it being very spontaneous, yet still passionate. I didn't write to-dos and tasks to be done, because there is always something to be done. And intuitively you feel what's important and what's not. I also didn't want it to "feel" like work.
For context - the game took me about 6 months to create: https://yare.io
No real process, no plan, no scrum method, not even a trello board to track progress and todos. Personally, I enjoyed the "fun" of it being very spontaneous, yet still passionate. I didn't write to-dos and tasks to be done, because there is always something to be done. And intuitively you feel what's important and what's not. I also didn't want it to "feel" like work.
For context - the game took me about 6 months to create: https://yare.io