Reading this made me miss BeOS. Blazingly fast UI. Mandatory to use separate threads for app rendering and processing user input to stay responsive under load. File system was implemented as queryable database with arbitrary metadata, so scanning for media was almost instant. Built in components for text rendering, media playback, etc, all had extremely performant implementation.
I remember easily playing half a dozen video files simultaneously, butter smooth, with the system still being instantly responsive as if it was doing nothing. On a 200mhz 603e. Those were the good old days.
HyperCard had some primitive reflection capabilities, where you could open a different HyperCard file and read its scripts.
I was pretty blown away when I used this truck to read in clear text the entire source code for Myst. Teenage me was pretty proud of myself.