You have to follow suit and trump when the talon is exhausted or when a player has closed the talon. In these cases, these additional rules come into play: any player whose turn it is has to
- take the trick with a (higher) card of the same suit as the card that was played. If that's not possible because the player doesn't have a card of this suit:
- play a lower card of the same suit. If that is also not possible:
- take the trick with a trump card. If that is also not possible:
- play any card
Please note: this means that following suit is more important than trick-taking. You cannot use a trump card when you could instead play a card of the current suit.