Check out as well:
- Vintage Firmware Modding Nokia DCT3 Phones video: https://www.youtube.com/watch?v=_7tkjJ-F95U
- video demonstrating various homebrew games: https://www.youtube.com/watch?v=APcUPL1Xb-o
- homebrew games and applications for old Nokia phones (including source code examples): https://sourceforge.net/projects/nokix/files/NokiX%20scripts...