Most rules are tied to particular elements of play, and in most games, the involvement of a specific rule is indicated by association with a color which can app

Most rules are tied to particular elements of play, and in most games, the involvement of a specific rule is indicated by association with a color which can applied as an accent to those elements. You can tell when en passant applies in chess because potential moves are clearly indicated, when poison is involved because the enemies, terrain, or even just the screen-vignette is tinted green. If you can integrate a color into the entities that are most directly affected by the rule in later situations, then players can infer the rules absence by the absence of the color indicator, which should stand out enough to be notable but be subtle enough to still look cohesive in later levels.