1. **Problem Statement:** Design a 5×5 grid maze with exactly one path from entrance to exit. 2. **Maze Design:** Consider a 5×5 grid where each cell can be open or blocked. The entrance is at the top-left corner (cell (1,1)) and the exit is at the bottom-right corner (cell (5,5)). 3. **Uniqueness Rule:** To ensure exactly one path, the maze must be a perfect maze, meaning it has no loops and no isolated sections. This is equivalent to creating a spanning tree over the grid graph. 4. **Example Maze Layout (O=open, X=blocked): $$\begin{matrix} O & X & X & X & X \\ O & O & O & X & X \\ X & X & O & X & X \\ X & X & O & O & O \\ X & X & X & X & O \end{matrix}$$ 5. **Path Explanation:** The unique path is: $$(1,1) \to (2,1) \to (2,2) \to (2,3) \to (3,3) \to (4,3) \to (4,4) \to (4,5) \to (5,5)$$ No alternative routes exist because all other cells are blocked, preventing loops or shortcuts. 6. **Trap Addition:** Add a trap at cell (4,4) that logically slows progress, for example, a "mud" cell that requires two moves to cross. 7. **Why Unique:** Since the maze forms a tree structure with no cycles, there is exactly one path from entrance to exit. Any additional open cell connecting two parts would create a loop and multiple paths. This design satisfies the problem requirements.