In the few games I tried, it always ended up that way. You start with a few prime numbers (if you're lucky). Each time you click on one, it gets replaced with another number that usually isn't prime. After a short while, there are no primes left and then there's nothing to do but sit and wait for the game to end.

Perhaps all the numbers should have a finite lifetime, after which they evaporate and a random new one replaces them.

Also, tiny nit but the text at the end says the largest known prime number has over 24 million digits. While technically true, the current largest prime number in fact has over 41 million digits!

(Also, I love this. I hope you’re still hosting it once I have kids)

I can confirm this bug - your random number generation algorithm should ensure at least one prime appears in each set, perhaps by maintaining a pre-computed list of primes within your range and guaranteeing inclusion of at least one.

Yep, got stuck with this too.