Just asking why the game window needs to be visible? It's webgame and pressing F11 puts it in fullscreen mode, this is practically the same for every other webgame that is played in a full browser. I'm just asking why the game window needs to be visible if going fullscreen is an option ingame that works on every browser like on my run here:

the game window edges are actually visible even on full screen at the sides?

Not everyone can speak french, so if this was decided in the discord, then I didn't see that sadly.

If this is to check which version of the game is being played, this could be put in as a tag somewhere in game (could be in the level menu or next to the timer - game UI suggestion).