Using the basic "Learn to Code 1" playground results in the MacBooks that I've tested on, including a 2020 MacBook Air, working far harder than I'd expect. The fans spin up and the CPU usage increases more than I'd expect.
The performance settles down if I leave the application running, I see the high load whenever I type and change the program.
The app is compiling some Swift code and displaying a fairly simple game interface to show the results. What can account for this poor performance on a capable machine?