Collect four-of-a-kind books. Most books wins.
Goal. Collect more books (sets of 4 same-rank cards) than the CPU.
Your turn. The rank buttons under your hand show every rank you currently hold — tap one to ask the CPU for that rank. They must hand over all matching cards. Catch them? You go again.
Go fish. If the CPU has none of that rank, they say "go fish" and you draw one card from the stock. If you drew the rank you asked, you go again. Otherwise it's the CPU's turn.
Books. Whenever your hand contains all four cards of a rank, the book is automatically collected and shown beside your hand. You can't be asked for cards in a book.
Ending. The game ends when someone runs out of cards and the stock is empty. The player with more books wins.