I have such a plan - but I didn't want to add thousand features in case nobody wants to play it.
Right now on my todo list there are two majors
1) colorblind friendlyness
2) making the gui loop fully idle when nothing happens
and I will want to add a level of the day soon afterwards if I see people are actually willing to play it.
And the reason why I went with the "campaign" as default is that the difficulty of puzzles differ tremendously so the gradual progress is better than one the same puzzle a day for everyone.
I’m a fan of a new puzzle every day.
Mix things up, some hard, some easier. Much in the way Wordle/Figure/Killer Crossword does it.
You don’t need to change your game, give a url that changes the puzzle every day.
People who want to binge can do it, people who want one-a-day can do that.