MPEG 4 Part 20 LASeR (ISO/IEC 14496 20) is a specification designed to deliver rich media services in a mobile environment. The specification is an emerging standard that can replace the MPEG 4 BIFS specification designed to deliver PC based heavyweight media contents. The specification describes the representation of scene information in a resource constrained mobile environment. Unlike the BIFS standard designed to deliver heavyweight rich media, the LASeR specification has a restricted description that conforms to the SVG Tiny 1.2 specification. Also, the specification has an advantage of allowing for the efficient conversion of one graphics format to another. In this paper, we present the design and the implementation of a LASeR authoring system that allows for fast and efficient creation of interactive rich media contents in a mobile environment. The Gill interface of the authoring system presented in this paper allows users, who do not have prior knowledge of the scene description language, to conveniently create contents and store the produced scenes using the internal list data structure. The system allows users to navigate scene objects internally stored and to create LASeR XML files in the structured XML format.