PhotoNeonFree is a drawing application for freehand neon art. You can either draw on empty space or draw on one of the photos that you've saved on your iOS device. PhotoNeonFree is a good way to add pretty colors, but comes with no instructions, few colors, and limited use outside of its intended purpose.
Neon colors are certainly eye grabbing, and so an app like PhotoNeonFree can be valuable for giving an image more pop. Adding neon to photos was a popular trend back when photo booths were in use, and can still be a way for iOS users to express themselves in their images. That said, PhotoNeonFree is fairly limited. There are only a few colors, there is no training (as soon as you open the app, you must figure out what to do next), and everything you do has to be completed with your finger, which is prone to errors. PhotoNeonFree also does not allow for layers to be deleted. If you decide you need to delete one of your lines, you need to undo everything else you've completed until you get back to the line you want to remove, causing you to delete all the lines you did like.
The colors in PhotoNeonFree are bright and attractive, and sometimes that's enough for the photos you're working with; plus, the app is free. But on most iOS devices it's too easy to make mistakes.