RAMbrandt

Replying to Scott above, it is true that the original RAT "mouse" (similar to TRS-80 Coco mouse) is compatible with Rambrandt, and any other art software that is also compatible with the Koala or Atari touch tablets. This is because both the original RAT mouse and touch tablets use the same inputs from the controller as Atari paddles. These are analog inputs. So you would just choose a Koala or Atari touch tablet from the choices the program offers for input and the original RAT mouse (or converted TRS-80 Coco mouse) work fine.

However, the later released Super RAT by Zobian is the more standard and common digital mouse, like the Atari ST and Amiga computers used. So the Zobian Super RAT mouse will not work with Rambrandt or other tuch tablet compatible programs. There are, however, other Atari art programs that are compatible with standard digital mice and the Super RAT mouse will work with them. These are generally PD art programs that aren't as widely known of as commercial releases however. But are covered in the Atari 8-bit FAQ under "software compatible with ST/Amiga mouse" section 8.6.

http://www.faqs.org/faqs/atari-8-bit/faq/section-1.html