Use signifiers to indicate the affordances of your game objects.
An affordance is a perceivable clue about what actions an object can afford. This will tell a user what actions they can do with that object. A signifier on the other hand is an additional layer of information that indicates affordances exist, such as a mark, sound, or label.
You should think about your player’s mental model when designing affordances and then suggest explicit actions by adding signifiers to your design.