Learning
Learning
tail recursive would be help
Use Xcode 10.1 to build and everything works well except the globe icon @brunophilipe 
But it broke the light mode, don't know why. 
The same on macOS 11.0.1, and after some clicks of dropdown menu & toggle theme, the interface nealy broken, mouse click not respond on most widgets.
+1, Thanks @treeder , rack-flash3 works!