With System 7.5, Apple introduced a new help system. Like Apple's previous help system, Balloon Help, Apple Guide is a radical advance in help system technology that will set the standard by which all future help systems are judged.
One of the most impressive aspect of Apple Guide is the coachmarks. As the system leads you through the steps required to do a task, it draws coach marks pointing out on the screen the exact object that you're supposed to be manipulating. This is a graphical help system for a graphic user interface. Take a look at the picture below for an example.
Coach marks are cool but they're hardly subtle (the exact opposite in fact), so what are they doing on this page? Well there are two very subtle aspects to how they're implemented. The first is that they are drawn slowly. This is a little difficult to demonstrate in a static picture [Hmm, I definitely need some QuickTime technology here! -- Quinn] but the coach marks are drawn slowly on the screen, as if the object in question is being circled by someone with a highlighter.
The second subtle aspect of the coach marks is that they are dimmed out when the appear behind the guide window itself. This is much better than the two alternatives, not drawing the mark or drawing the mark in full, thereby potentially leading the user into thinking that the designated object is on the guide window.