Opaque Interfaces

I love opaque interfaces, and find them attractive to look at and think about. My favorite opaque interfaces are command line applications like programming language shells or text adventures. Much like any piece of text, their meaning is revealed slowly, upon further inspection. This is a really nice effect and it allows a work to stay with you longer. I've never finished Zork but I think about it all the time. I wonder if hypertext is more or less opaque than a command line. What does a parser really do?