This site was designed to function as an "on the go" (i.e. built for mobile platforms) flashcard system for basic arithmetic. The primary purpose of this site was to allow me an easy to use practice space for Vedic math.
The operation pages utilize an HTML 5 canvas element, and allow drawing markup on the problem with either mouse or touch screen (click the "Draw Mode" button to toggle between drawing and pan/zoom). The difficulty of the generated problems can be adjusted by opening the options pane when inside an operation page.