Designers should always look to avoid having a ludonarrative dissonance in their game. A ludonarrative dissonance occurs when game's narrative contradicts it's gameplay. In other words if a developer were to create a game where the main character is considered to be a morally good person (narratively speaking) yet the character due to the player's actions is allowed to do morally reprehensible actions, this would be considered a ludonarrative dissonance and can pull the player out of the game. Games that place an emphasis on player choice in regards to the narrative can often fall victim to this if the developers are not careful and don't design their game with certain outcomes to fit the player driven narrative.
Example 1: Mass Effect[]
The Mass Effect series is beloved by many (myself included) but has a perfect example of ludonarrative dissonance lurking within it's story. Mass Effect allows the player to make many choices through out it's series which dictate how further storyline elements will unfold and can even effect the main character's appearance. However all these decisions are quantified and qualified on a scale between two opposing positions of paragon(good) and renegade(bad). However if a player were to go 100% renegade and be as completely self serving, ruthless, and vile as possible, they would definitely look the part but the narrative would continue to refer to the main character as a great hero with no mention to the horrible things they had done. In a way the narrative completely undermines the player's decision to be "bad" as the narrative will seemingly portray them as a great person.
Example 2:Prototype 2[]
In Prototype 2 you play as James Heller who is out for revenge after his family was killed by the Blacklight virus. How does he go about his revenge you may ask? By killing and infecting more innocents with the same virus that killed his family. It would make sense if he kills the people who created said virus and not innocents but this ludonarrative dissonance completely negates the main character's back story and ruins the experience of taking revenge for your family's death.
