Of all the apps I've built, perhaps my favorite is https://git.sr.ht/~akkartik/snap.love, my box and line drawing tool. I use it _constantly_ -- including for work. I have a terrible short term memory, and now I make quick mindmaps for every little situation where a full-screen IDE on a huge monitor is too tiny to show all the parts of the codebase I care about right now.

I seldom mess with it, but today I modified it to show gridlines any time I drag things around. Should lead to neater maps!