Every year when I participate in advent of code, I have this thought: "wouldn't it be great to solve these problems directly from my phone?" (The puzzles unlock quite early morning in my timezone and opening my laptop at that time somehow annoys me.)
I have wondered many times if some structural editor with a bunch of high-level library methods (Dijkstra's, for instance) would actually give a good/fast experience for most days. I haven't had the time or interest yet to try and build something yet. But perhaps I should.