I've got it.

The cards are shuffled into one big pile, from which each player gets three cards.
The goal of the game is either to be first to fifteen points, or have every other player drop to -15.

On each player's turn, that player has four choices.
1. Draw a card
2. Use a card in your hand (+ cards add points, - cards subtract points from other players)
3. Use a prism card
4. (If you have no cards in hand) Draw two cards

When a card is used, it gets shuffled back into the pile.

This way, I have made the third nipple card useful, another player may get bad luck and take it from another player using the prism.