Yo, 'sup!
This doesn't seem like a bug, but rather a discussion on optimization, so I'll move this thread into General.
As for the issue itself, I could definitely optimize some things a bit, but the majority of the situation you're seeing here seems to be unrelated to MasterPlan itself. It seems like the CPU usage being high is a peculiarity with the graphics framework I'm using (Raylib), as I believe it uses a wait loop to idle when waiting for the next frame to draw. Even with drawing and updating an empty window, I'm getting similarly high results when checking the CPU usage on Linux. I'll see about tweaking it to use VSync as a method to handle its timing - this seems to improve the CPU usage.
Keep an eye out for that update in the short-term!