St. Patrick’s Pattern Builder is an interactive St. Patrick’s Day math game for kindergarten through third grade students that invites learners to construct their own repeating patterns using shamrock, gold coin, and rainbow cards. Five difficulty levels — AB, AAB, ABC, ABBC, and AABBC — let teachers differentiate in real time, while a built-in structure validator checks not only that students have placed enough cards but that every unit correctly repeats the opening sequence, supporting genuine pattern understanding rather than surface-level imitation. A hint system describes the target pattern in plain language, and a progress bar motivates students to build toward the minimum length. Aligned to Common Core Standards for Operations and Algebraic Thinking (K.OA, 1.OA, 2.OA) and state math standards for pattern creation and extension, St. Patrick’s Pattern Builder works equally well as a whole-class warm-up, a math center activity, or a family engagement tool at home.