Simple interface, simple switch to go through Light or Dark Theme whenever you want and when you reopen the app you'll use the same Theme you were using the last time you closed it.
Make it easier to write like a BM would do: write the text in the box you'll find on the foreground of the application, tap on the CONVERT button and you'll find the text to copy just by tapping on it! And if you don't like how the app converted the text, just re-tap on the button!