Cheat

Cheat is the card game where the cards are face down and the only thing anybody can go on is your word. The whole deck is dealt out between three players. On your turn you put one to four cards face down on the pile and say what they are, and the rank you say has to be the one already on the table or one either side of it. Everybody can see how many cards you played. Nobody can see what they were.

That gap is the game. Sooner or later you will not hold the rank being asked for, and you will have to put something down anyway and call it a three. Any other player can say so, and the cards get turned over: if you were lying you pick up the whole pile, and if you were not, they do. The first player to get rid of every card wins, but only if nobody calls the last one.

It is also known as I Doubt It and as Bluff. You play two computer opponents at three strengths, or deal a table to two friends over a link. The pile is genuinely hidden here rather than merely not drawn: your browser is never sent the cards that are face down, so there is nothing to peek at even if you go looking.