Thanks for the review, and for these tips.
Apologies. The readme has now been updated to reflect all the sources, including the snippet of your code I used for generating the wallet. Didn't find the time for it before (you know... postponing documenting things).
I have also added a note about offline usage. Which does work out of the box, both through save page, and through checking out the code from the git repository.
You can see the readme here: https://github.com/norbertvdberg/iotaseed/blob/master/README.md
- As for mnemonic words. If the user saves the page and his mnemonic seed, there is no reason not to use them while there is no official way. That is how tech progresses. Also the paper wallet for long term storage that was added, lists the private key as well, so does not require them.
Of course it is everyone's own decision, but I would say https://iotaseed.io with it's mouse based entropy is a lot safer than most other solutions based on system entropy. I built it for my own use, and whether others wish to use it is up to them.