LOL, that's a new game genre I came up with. ;-)
I wasn't aware of the issue but with unity 2020 there is a bug when building a WebGL game, see this link for more informations :
https://itch.io/t/912627/unity-webgl-game-wont-fully-load
And since the rating has already begun, I can't upload another build.
Anyway, thank you for your coment. :-)