Sum Lines is a strategic number-path puzzle in which students place given numbers onto one or more number paths, sometimes overlapping, to reach a target sum. Each level begins with a starting value and a goal number, and players must decide which numbers to use and where to place them so that each path’s total matches its target. When two paths overlap, any number placed at the intersection contributes to both sums, encouraging students to reason about shared values, efficiency, and the structure of the puzzle. Early levels focus on positive integer addition, while later challenges introduce negative numbers, prompting students to think about how to move toward or away from a target value. Because not all numbers must be used, students develop flexibility, problem-solving, and strategic thinking as they test combinations, analyze pathways, and make sense of how numbers interact across connected lines.