You start with one shuriken as well, and if everyone wants to use a shuriken, each player discards their lowest card face up, giving everyone information and getting you closer to completing the level. As you complete levels, you might receive a reward of a shuriken or an extra life.

The trick is that players can't discuss anything about their own cards, or as the rulebook says, no sharing of information, no secret signs.  In the event of a misplay  because a player has a card in their hand lower than the card just played  gameplay stops. All lower cards are discarded, and the team loses a life.