Hi Marcus, Yes I've been aware of STACK for a while, but I've only started to take more interest since I joined moodle.itemspro.eu. I also discovered jsxgraph there, which is also very interesting. My impression of both is that they are powerful but not particularly user friendly. Maybe I'm wrong.
Regarding STACK, my Moodle provider does not provide a MAXIMA pool server which I understand is required. I've no idea as yet how to link to a MAXIMA pool service, if that is possible or how to go about it. Perhaps I'll explore further when I have time. Best wishes Dave