About Gemini Tricks, from BoardGameGeek:
Bring your own deck of cards to play a duo of trick-taking games featuring a shared setup where you split your hand into two smaller hands using the included Gemini cards - Pollux and Castor.
Pollux is a trick avoidance game. In this game you split your hand, choose a pain suit, and a wood taking points. Trick play is must follow suit or ensure two suits are played to a trick - there is no trump. High cards cancel each other out, leading to surprising twists. The Pollux card must be played during the second split hand, and is +.5 of the prior card value in your pain suit. Also features a team play variant.
Castor is a must follow trick taking game with a permanent trump suit and a shoot the moon mechanic. To begin, pass cards and split your hand into two. No bidding needed, take 3, 4 or 6 tricks. The Castor card may be played at any time and is +.5 of the prior card value but in the lead suit.
-description from the publisher