Connect ball collection to the enemy at the path's end.
Growth has a stated purpose
Monster Transformation describes moving a snake left and right, avoiding obstacles and collecting colored balls to become large enough for a final enemy. That connects the collection section with a later confrontation. Read the actual scene to see how growth is recorded. The source does not provide a required size threshold, color rule or exact relationship between a collected ball and the final outcome.
Compare a collection path
When balls appear near an obstacle, consider the route through them as well as the possible growth. A pickup that looks useful may require a correction that leaves the snake poorly positioned. Choose based on the usable space you can actually see, not an invented assumption that a particular color guarantees a larger reward. Follow the active control instruction for moving left and right.
Check what reaches the final encounter
At the end of the path, inspect the state the game carries forward and the requirement it presents. A visually larger character does not by itself establish a guaranteed win. If the attempt fails, separate collection choices from misunderstandings about the encounter's action. This note offers no tested ball route or enemy strategy. It helps keep growth, obstacle avoidance and the stated final goal part of one readable decision sequence.