We built Guidants, a stock market tool. It needed to be something close to an operation system. Capable of finding & launching different apps fast, combining them, administrating them. Windows needed to be draggable, but without the hassle of placing them correctly. Each having their own navigation, settings & scale. These are problems that operating systems face. On top of this, it needed to work & be usable inside browsers. So it needs to deal with different resolutions, different browsers & different customer expectations. This talk is about the many tough challenges involved, some of which we solved and others we're still pondering over. Come join us on this adventure!