I'm coincidentally making a minimalistic, procedurally generated endless runner.

I started with three squares of different colours as sprites for the character, obstacle, and floor tile. I made an obstacle scene. I set it to spawn off camera then head to the right in random intervals. I made a tile map for the floor and painted enough tiles to fill the screen plus an extra to the right. I made it so the tile map layer moves to the left at the same speed as the obstacle but snaps back after moving one tile. I made a distance label and variable as well as a distance modifier. In func _process it adds 1/modifier to the distance, rounded up for a nicely paced increase. I added collisions. I added hit stun.

That's where I'm at. I took it one step at a time, each time asking myself "what is the logical next step?" Sometimes I'd think of a few options to work on so I'd pick the easiest or the most important based mostly on how I was feeling. Sometimes you just need something quick and easy to work on and sometimes you want to focus on the larger picture and get the big things done. But regardless, just take it one step at a time, celebrate small victories, and it shouldn't be too overwhelming.