Level 1: Empty Box
Level 2: Internal Structures
Level 3: **Recursive Box1 ** (If go out of box A to B and find that the target point is a box C that cannot be moved, you should directly slides from A into C with the round position)
Level 4: the same as Level 3
Level 5: Multiple reference
Level 6: Greedy Snake
Level 7: Recursion Overflow In
Level 8: Recursion Overflow Out
Level 9: Implementation of Basic Sokoban Rules
Level 10: small test