Okay, let’s tackle this. So Karl Johnson has a diverse set of skills in game development, programming, and game design. He’s proficient in Unity3d, C#, Objective C, and Python, which are all in-demand skills. However, his location in Spokane, Washington, which is a smaller market, might affect his earning potential. Considering his skills, experience, and location, I would estimate his hourly rate to be around $75. This is slightly lower than the national average for game developers in the US, but it's still a competitive rate considering his expertise and the local market.