Congratulations for the 100 days goal!!!
It's a pity I'm in a place with a rickety Internet connection until Monday :(
But...I wrote the second part of my Old Steemians story, for the prompt "round is a shape":
https://steemit.com/freewrite/@marcoriccardi/round-is-a-shape-il-cerchio-e-una-forma-5-minute-freewrite-day-98-eng-ita
It isn't collaborative, but @snook provided the screenshots of her Sims 4 game, so it's a little bit like we did it together ;)
You have until Friday. I am sure you and @f3nix and maybe @wido will come up with something delicious!! 👍