In Scratch 3 you need to click the arrow button to make the program larger before it runs properly. 1. Shift-click the flag to enter Turbo Mode and then click the flag to run the program 2. Move the mouse-pointer over a white area inside the maze and press the spacebar to begin The sprite will find its way out of the maze. Try changing the background to a different maze (you might need to change the program if the maze is a different colour), or adapting the program to see if you can make it faster and/or smoother.
The new National Curriculum for Computing requires discussion of "computational abstractions" and algorithms. This program takes an idea that most students are familiar with. The computational abstraction is the method you would use to find your way out of the maze - e.g. following an edge - and the algorithm is the way you do that - e.g. moving to the left until an edge is encountered, and then turning back a bit and moving forward.