With pleasure. Coinglacier.org uses cryptographic secure random numbers provided by your browser: https://developer.mozilla.org/en-US/docs/Web/API/Crypto/getRandomValues . This should be safe. However, as an additional security measure, we add more entropy on top of this, in case there is an unexpected flaw in your browsers implementation of Crypto.getRandomValues(). This is the part that is time consuming at the startup of the page. We do this through the use of the NPM package "more-entropy": https://www.npmjs.com/package/more-entropy

What it does is it runs some calculations in the background and measures the time used for each calculation. The resulting times are then used as the additional entropy which we XOR with the entropy from Crypto.getRandomValues().
This is basically the counterpart to moving your mouse around on bitaddress.org .

Hmmm.. interesting. Is it only the QR codes that takes long to load or also the addresses and private keys? Also, does it only happen when you password encrypt your private keys? In the case that would be normal, because the BIP38 decryption is rather resource consuming by design. This is not a bug, but a feature. Since the procedure takes so long, it is much harder for an attacker to brute force your password.

That could easily be implemented if people desire it. The idea was to have a very easy "single wallet" page, without all the options and leave the more advanced stuff for the "paper wallet" page. Of course you can also generate a paper wallet containing only one single address there.