“Easter eggs”
This example shows how to hide material from viewers. Menu 1 contains a button that is invisible to the viewer unless the viewer accidentally selects it — for example, by playing the DVD on a computer and moving the mouse over the button. This is done by setting the button’s opacity to 0%. The button links to Movie 2, and is the only way that a viewer could get to see this movie.
Another way to hide such a button is by having no subpicture on the button (the subpicture is an image that changes color and opacity when the button is selected and activated). If the button has no subpicture, viewers cannot tell that it is a button; all they will know is that the button selection has disappeared.
Some DVD authors don’t hide material with invisible buttons, but design their projects so that the viewer must watch the main feature to its end before they can see the extra material. In this example, the button that links to Movie 1 does not have a link end action. Movie 1′s own end action links to a “special” menu (Menu 2), which can only be seen if the viewer watches Movie 1 to the end. If the viewer gives up and presses the remote control’s Menu button or stops playback before Movie 1 finishes, they will never see Menu 2.