The Jasik Debugger (or more correctly, The Debugger from Jasik Designs), was a debugger tool for the classic Mac OS. Pitched as a much more powerful alternative to Macsbug, it was the debugger of choice among professional Mac developers until the advent of more advanced source-level debuggers such as that built into Metrowerks Codewarrior.
While Jasik's debugger featured a graphical user interface, it was laid out in a very arbitrary and peculiar way, with buttons seemingly randomly sized and positioned. This gave it a reputation as difficult to use.