This is the big one, the one the whole story twirls merrily around. Tan makes chess a mysterious force and lets Waverly gain confidence from "the secrets I found within the sixty-four black and white squares" (28). Like a Jedi knight, Waverly gains power from chess, to the point where she makes a grown-up opponent sweat like a racehorse. No, really—"his sweaty brow seemed to weep at my every move" (49). You go girl, right? Chess helps Waverly get out of chores and it makes her famous, all just for being really freaking good at the game.
Unfortunately, though, chess also takes away the other things she used to do. By focusing so much on the game, Waverly loses everything else in her childhood, to the point where she doesn't really have any childhood left.
Tan's pretty subtle about this point, though she makes a quiet reference early on when Waverly "carefully drew a handmade chessboard and pinned it to the wall next to my bed, where I would stare for hours at imaginary battles" (28). Then later, chess seems to block out the details of everything else in the world, like when "The boy disappeared, the color ran out of the room, and I saw only my white pieces and his black ones waiting on the other side" (38). Waverly gains a lot, but chess takes a lot from her as well—checking her out of the rest of her life.
Perhaps even more importantly, though, chess works as a giant metaphor for Waverly and her Mom. These two are constantly engaged in head games, trapped in a battle of wills and trying to figure out how the heck to come out ahead. Again, Tan's pretty sneaky about the comparisons. She lays a seed when talking about the chess moves Waverly learns:
I went to school, then directly home to learn new chess secrets, cleverly concealed advantages, more escape routes. (51)
She then uses the same phrase to describe Waverly's own fraying relationship with her mother, writing, "The alleys contained no escape routes" (62). It's clever, and it lets us know that chess = life in Waverly Land, which is perhaps due to the relationship she has with her mother. In a way, Waverly was playing chess before she'd ever heard of the game, and once she starts playing, the lines between the game on the board and the game in her life blur. Instead of getting her mom in checkmate, though, Waverly finds herself trapped, uncertain of her next move.