You can check the free online-version of the twenty frame at www.lernsoftware-mathematik.de/prototypen/zwanzigerfeld.html before
The learning tool provides a virtual math manipulative for exploring and understanding basic math operations (addition, subtraction). You can manipulate the virtual double-sided counts in a five-structured twenty frame and observe the effects to the addition or subtraction term. Over the observation and manipulation of multiple representations the child gets a (deeper) unterstanding of the basic math operations. This helps especially children with dyscalculie..
To see how to use the twenty frame and all it's possibilities, watch the video at: http://www.youtube.com/watch?v=mWAxGLGoVDo.
The virtual tool doesn't provide tasks, but it can be used to solve and visualize school or homework tasks.