From the announcement trailer, Pokmon TCG Pocket seems to have been built in the same mold, a free-to-start game where you collect cards and challenge other players to quick and breezy battles
If Yahenni and a creature an opponent controls die simultaneously (perhaps because they fought or were in combat together), Yahenni won't be on the battlefield as its triggered ability resolves
It's Temur (green/blue/red), which are some of the best colors for artifact decks
Strategic complexity This is not only fine at common (provided it doesn't have one of the other two types of complexity) but encouraged, as it helps to create depth for the more advanced players
Fun fact: Skorupi glows in the dark, making it a dazzling sight during nighttime adventures
Of course, it's very possible that the next batch of battles are just sieges again, but the designers left themselves open to possible variations