itch.io

Games that try to simulate real-world activities (like driving vehicles or living the life of someone else) with as much realism as possible. Simulators generally require more study and orientation than arcade games, and the best simulators are also educational.

Resources relating to or for building Graphical User Interfaces (Commonly called GUIs)

Pretty sure everything is indie on itch.io but just in case you want something extra indie.

Resources for building and relating to User Interfaces, how the user interacts with your program