Almost all projects start that way as some small learning project. You usually do not build complete applications in 1 day. You usually lean heavy on existing

Almost all projects start that way as some small learning project. You usually do not build complete applications in 1 day. You usually lean heavy on existing libs or chunks of code you already learned somewhere else. That is what that sort of thing is for. In my 26 years doing this most of what I have written has been thrown away. There may still be some bits here and there living on but I doubt it. Yet at one point all of that code had a use and did it well. That use was me using that knowledge to get things done. Those prototype projects do a lot of that sort of thing. If I wanted to make an scala version of my 'basic editor' it would probably take me at least a week of digging through docs and trying things. But in another realm I can bash it out in a couple of hours. My point was your domain knowledge is what makes you a better developer.