Area-based planning processes are rapidly moving from paper and desktop GIS based processes to online applications offering real-time analysis and feedback. Users want an interactive and informative experience allowing them to generate reports and analysis without needing to understand the subtleties of GIS or spatial analysis. They expect a compelling user experience that works on a variety of platforms Ð ranging from old or outdated browsers to tablets and smart phones.Building from years of experience (and standing on many shoulders), this talk demonstrates some of the strategies and techniques achieved for the Marine Planner platform, an online open-source map viewer and decision support tool. These strategies include UTFGrids, tile caching, pre-processing, and standard and forked OpenLayer libraries, among others. The result is large-scale scenario planning tools with a responsive and compelling user-experience that anyone who has used online maps can figure out.