I've been looking for an app where I could quickly write stuff (or erase stuff). This one definitely delivers! Super easy to use, pretty intuitive.
The only things I would change is:
1) Add a zoom function for easier drawing in tight areas
2) Add an extra fine pencil for precision drawing
3) Move the eraser and reverse/back button away from each other.
4) The save button was confusing. When you click it, it was in Spanish and I didn't know it saved, so I clicked it again. Maybe make that notification bilingual or put a check mark ✅ in the dialogue box.
If these were done, I would definitely pay to buy the app to remove ads :)