Favorite writing / journaling tool? Half-finished projects welcome

I’m specifically looking for a tool a user shared on here that facilitated writing for content by scrolling up and disappearing text as new text was inputted. I believe it was a HTML/JSS only solution - a small personal project. I’ve done a lot of focused searches, but haven’t been able to find this comment. That said, I love these sorts of projects. I know they’re a self-indulgence and often a distraction. I’m celebrating that for a moment, personally. Please share your favorites writing tools, the smaller and more personal the better.