Everyone gets five dice, rolled secretly into your phone. That's your cup. Guard it.
You're bidding on the whole table's dice combined. "Four fives" means: among ALL cups together, there are at least four fives.
On your turn, raise the bid (more dice, or the same number of dice at a higher face) or cry LIAR on the last bid.
LIAR means cups up: every die is revealed and counted. Ones are wild: they count as whatever face was bid.
If the bid was true, the challenger loses a die. If it was a lie, the bidder loses one. The loser opens the next round.
Lose all five dice and you're out. Last cup standing wins.
Scoundrel's wisdom: your own cup is your only truth. With 4 players there are 20 dice, so about 3 of any face exists before anyone lies. Bid what you hold. Lie about the rest.