GUI
- add an interactive vigenere-square that highlights the column and row you're clicking on. (a.k.a. animation)
- Less compact UI
- Resizable/responsive GUI
- Move to JavaFX for a richer UX
- Add a drag and move functionality instead of clicking on the arrows for rotating the wheel
- Implements Google Material design API for the UI
Cryptography
- add the enigma as encryption / decryption
- add functions that make cracking codes easier
- add a section with user defined cryptography functions
- add comparison of time needed to break encryption
- add timeline of popular encryption schemas and their relevance
- add password strength measurement functionality to estimate time to crack
Other stuff
- translate the program in other languages
- add build instructions
- Code examples in python
- Set MonkeyCrypt icon as the app icon instead of the default java applet icon
- Pseudo-intelligent assistive agent similar to clippy for Microsoft Office 2003/2007 that helps children to get hints.
- Put some examples in the help section for each cipher (ex. In Caesar's cipher it would be much easier to understand if a word like 'CAESAR' is converted to corresponding cipher text).