Mobile learning games (MLGs) have great potential in education , especially in fields requiring outdoors activities such as botany or cultural heritage education. However, the number of mobile learning games actually used for outdoor education remains very low. The absence of dedicated applications allowing to build MLGs, without technical expertise , is certainly one of the most important factors. To overcome this limitation, we propose a design method for MLG authoring tools, based on reusable components. We describe in this paper the design and first results of Moggle-Designer, a full-web MLG authoring tool requiring no technical expertise. We detail how a model-based approach, combined with component-oriented programming, adequately allow the representation and manipulation of didactic expert knowledge. Finally, we present Moggle-Player, an application for running the designed MLGs on any mobile browser. Moggle-Designer was used to design several mobile games that have been tested during a pilot study in a botanical park.