Comment by bitwize

The card game in Yu-Gi-Oh had "rules as the plot demands", at least during the seasons with Yugi and Yami-Yugi.

When they released the real-world Dueling Monsters card game, they tried to keep the rules consistent with the manga/series, but changed them in places to make a more playable game. Ex.: there is an upper limit to the damage you can do with the Berserker Soul ability.