Please have a play with this online prototype.
I've made animated GIF images of the capital letters A-Z and numbers 0-9. These are paired with a sketchpad where the shapes can be made by the learner. This automatically clears itself every 4 seconds.
To allow a very rudimentary sequencing, clicking on any of the examples or headings makes that example (or heading) disappear, so the learner can see the next one better.
I've arranged the letter shapes in "shape order" rather than alphabetical order. Thus the learner can start with the simplest one: a vertical line.
And then move on to more complicated letter shapes:
The numbers are introduced with "guide dots" which show the quantity "covered by" the shape:
I find this prototype almost works on an Android phone and an iPad (Chrome). The sketchpad only clears when you click to dismiss an example.