Use blocks from the More Blocks tab, the Control tab, the Looks tab, and the Sensing tab to make a program that moves Sidney from start to end. Now that portal exits are not always colored, you'll have to use the Sprites menu to identify which sprite Sidney is touching at each of the portal exits. Then, "if" blocks can be used to take Sidney from each of these portal exits to the finish along a unique path.
Based on a design from MyCS_Student and the work of the students at Harvey Mudd College.