Objectives. In this thesis I have, together with game developer and publisher Paradox Interactive, designed and implemented a level editor tool for use in their game Magicka 2. With this tool users can create, edit and share custom Challenge levels in the game. I have also done a more in-depth scientific study of usability in such level editor tools, especially pertaining to the disparity between various controller input schemes and platforms. Methods. I have performed a literary study of articles and books relevant to the field of game design, user interface design, general usability, controller input schemes and any other topic I found relevant. I have paired this with a study of similar level editor tools and their user interfaces and features in other console and PC games. This knowledge, together with feedback from both expert and non-expert testing, has then been analyzed and used to design and implement both the user interface and the features of the level editor. Results. Results of the literary study, level editor tool study and testing are presented together with their impact on the design of the user interface and all implemented features. The results of each iteration of the Challenge Creator are presented as well. Lastly, all results are analyzed and a set of design heuristics for creating a similar level editor tool is presented. Conclusions. I conclude that creating a platform independent level editor tool with high usability is very much possible, but that designing such a tool becomes far more difficult with each new platform and controller input scheme supported. I also conclude that additional features and further increase in tool complexity loses significant impact if the core user interface is lacking in usability. I also conclude that more time and testing will be needed to further empirically validate the design heuristics. Lastly, I conclude that additional iterations will be required upon the Challenge Creator to improve its usability in light of already known and established design flaws.