ruff is your pocket-sized best friend that aims to make writing on the go fun, and sharing it fast & easy. Don't take my word for it:
"If you like to write and wish you could do so from your Android device without any distractions, then look no further than ruff. The app contains both a light and dark theme, and it even works on Chromebooks, which makes it a great option for portable writing. Saving your content is easy. All you have to do is swipe to the right, and the app will save your progress so that you can easily pick up where you left off, even if you switch to a different Android device." — Android Police
"It’s a bit of a niche product, but it looks nice and it works as described." — Android Authority
The free version is ad-supported. Upgrade to ruff+ to remove ads, and to also enable the ability to set aside (aka stash) text to come back to later.