Huangdi has 2 main features. In the base game, look out for a full symbol stack on the first reel which will expanding all matching high symbols on the other reels. The matching symbols will only expand though when part of a winning combination.
In the Free Spins feature which is triggered when you get 3 or more golden dragon scatter symbols anywhere on the reels. This will reward you with 15 free spins which can be re-triggered if you get 3 scatters during the feature itself. The feature benefits from stacked and expanding wilds to potentially give you huge wins.