Each player finds words from the letters of sequentially adjacent cubes, where "adjacent" cubes are those horizontally, vertically, and diagonally neighboring each other. Words must be at least three letters long, may include singular and plural (or other derived forms) separately, but may not use the same letter cube more than once per word. Each player records all the words he or she finds by writing on a private sheet of paper. After five minutes have passed, all players must immediately stop writing and the game enters the scoring phase.

To score the game, each player reads his or her list of discovered words. If two or more players wrote the same word, it is removed from all players' lists. Any player may challenge the validity of a word, in which case a previously chosen dictionary is used to check if it is a word. For all the words left after duplicates have been removed, points are given based on the lengths of each word. The player with the most points wins. If there is a tie (two or more players with the same score), break the tie by counting the number of long words.

One cube is printed with "Qu." This is because Q is nearly always followed by U in English words (see exceptions), and if there were a Q in Brainstorm, it would be challenging to use if a U did not, by chance, appear next to it. For the purposes of scoring Qu counts as two letters: "squid" would score two points (for a five-letter word) even though it uses only four cubes.