Kaleidoscope is (was) a Macintosh Operating System GUI customization extension, which alters the elements and settings the pre X (10.0) MacOS uses to draw the GUI.

The process of 'scheme' creation involves a fairly time consuming process of mucking about with ResEdit and a special set of templates that allow for the editing of the special definition resources the extension uses. These settings define certain relevant areas of multiple image resources, usually abnormal cicns created most frequently by use of a hex hack to the ResEdit code to allow it to manipulate nonstandard cicn sizes. These defined areas are then patched according to and along with the other settings to running MacOS.

Amazingly enough this caused relatively few crashes, normally only taking down the system once every 150 patchings or so, an issue only to the very indecisive, or those already masochistic enough to go through the process of 'scheme' creation.

The patched drawing protocols usually had no noticeable effect on performance, unless they were excessively heavy, complex, or just plain badly made, in which case they could prove very slow (and since inefficient ones were normally fairly bulky were really not practical to work with on a daily basis any way).

Given the completely different system post MacOS X uses for drawing the GUI, Kaleidoscope is completely unportable. Also Apple's present attitude makes it seam very unlikely that any similar product will exist for MacOS X at any time in the near future. One such project was started and the creators of the tool were heavily threatened with legal action over reverse engineering proprietary Apple technologies. An action which has been laughed at, scorned, and supported by those who have had one to many doses of the Jobs Reality Distortion Field.