This looks awesome. The way you are dragging things around and the diagonal lines is amazing. Don't think asciiflow or the other one or two tools do this.
Since you are providing a single portable html file (which almost no one does that these days sadly) you may be interested in how sequencediagrams.org handles this. They don't offer sign up, instead have localStorage, Google drive, file export and few other ways.
Also, can you let me open it on the phone with a warning/recommendation to look at github instead of redirecting to it.
Bit of a nightmare getting this elegant enough on a phone, and doubt anyone wants to draw ASCII digrams on their phone anyway, so not really a priority!
Since you are providing a single portable html file (which almost no one does that these days sadly) you may be interested in how sequencediagrams.org handles this. They don't offer sign up, instead have localStorage, Google drive, file export and few other ways.
Also, can you let me open it on the phone with a warning/recommendation to look at github instead of redirecting to it.