Please answer a question about the following article about IPod:

Apple's application to the United States Patent and Trademark Office for a patent on "rotational user inputs", as used on the iPod interface, received a third "non-final rejection" (NFR) in August 2005. Also in August 2005, Creative Technology, one of Apple's main rivals in the MP3 player market, announced that it held a patent on part of the music selection interface used by the iPod line, which Creative Technology dubbed the "Zen Patent", granted on August 9, 2005. On May 15, 2006, Creative filed another suit against Apple with the United States District Court for the Northern District of California. Creative also asked the United States International Trade Commission to investigate whether Apple was breaching U.S. trade laws by importing iPods into the United States.

Which competitor sued Apple over rights to part of the software user interface?
Creative Technology