Indeed. I got curious how the display works, and apparently in the circuit there are just labeled nodes, and in the frame with the display the simulated CRT is

Indeed. I got curious how the display works, and apparently in the circuit there are just labeled nodes, and in the frame with the display the simulated CRT is just a bit of JavaScript looking at the voltage of those nodes (going to the next line or frame based on the voltage on the respective sync signals, monochrome CRTs are very simple in that regard). That's enormously cool, I do use the falstad circuit simulator, but I've never thought I could add a separate frame with JavaScript for I/O.