Note to forums... I may be copying this often
Since you've made text-based games, I believe you should go to 2D land. Here's my suggestion on how you should progress.
- Space Invaders (credit to GearSlayer360)
- Missile Command
- Tic-Tac-Toe (credit to 3Ddreamer)
- Make Money
The reason for this list is because you know how these games work. The rules and how all the parts are supposed to work. So it's easy to go down the list and learn new skills as you complete each game. For a really good tutorial on 2D game development, google for Lazy Foo SDL