Mathigon – an interactive, personalized mathematics textbook
Some feedback:There is no help if I get something wrong.  E.g. on the last question on https://mathigon.org/course/graphs-and-networks/eulers-formu... I did not understand the final section's explanation (I have no idea what "the topmost face of the polyhedra becomes the “outside”" is supposed to mean!).  I tried entering a number into the last box and it was wrong.  I entered another - wrong again.  The "chat" thing just said "try 2" and it was right.So why was it 2?  There was no explanation or more help to explain that to me.  I was just told to enter 2 and I did without anything to help me understand more, and then it let me continue.It would be useful if, when someone gets the answers wrong once or twice, that some extra material appears, perhaps with more examples or more step-by-step explanation to help explain why.  No need to show this to everyone - only show it if people are struggling or click on a "tell me more" type expandy thing.As it was, I still do not know why the answer was 2 and I leave mystified and frustrated.Otherwise its very nice - one or two weird moments where I had to click on "reveal all" on Firefox (appears to have not realised I scrolled?)