Tricky. Being an effectively dead system (although there are live descendants), there aren't a lot of live resources. You might get a feel and some information from http://www.digplanet.com/wiki/HyperTalk or http://edvista.com/claire/hypercard/index.html . I think the important paradigms (many of which you're already familiar with and use regularly) are the object oriented, dynamically typed nature of it, the subject/object/verb 'natural' syntax, scoping of variables, and event handling. http://www.amazon.com/dp/0966551427/ was the 'bible'. And http://www.youtube.com/watch?v=H5-T_S50Sr4 is a fun demonstration.