Tried Challenge 1, "Two very different afternoons", in the browser. "The cat is sleeping while the dog is chasing butterflies" was accepted. The two separate emoji lines made the roles clear, and the explanation after solving it was useful rather than just a green tick.
One tiny first-run snag: the challenge picker says "Equivalent sentences count", but the puzzle immediately asks for a 10-word story. I wasn't sure whether there was room for different phrasing or only a different order. A short example of an accepted alternative would make that promise easier to understand.
The cat has the better afternoon, obviously :)