Sure, I can help you generate a test case for the problem statement "Mirror Labyrinth." Since the problem statement is incomplete, I'll make some assumptions to complete it and generate a test case generator accordingly.

### Assumptions to Complete the Problem Statement:
- The map is a 2D plane split by a straight vertical line at \( x = M \).
- Each building is represented as a polygon defined by a list of vertices (points in 2D).
- The points of the polygon are given in a specific order (clockwise or counterclockwise).
- The input will consist of:
  1. An integer \( M \) representing the x-coordinate of the vertical dividing line.
  2. An integer \( B \) representing the number of buildings in one area.
  3. For each building, an integer \( V \) representing the number of vertices of the polygon, followed by the list of \( V \) points in the form \( (x, y) \).

**Input**
1. An integer \( M \) (the x-coordinate of the vertical dividing line).
2. An integer \( B \) representing the number of buildings.
3. For each building:
  - An integer \( V \) (the number of vertices of the polygon).
  - A sequence of \( V \) pairs of integers \( (x, y) \) representing the vertices of the polygon.

**Output**
For each building, the mirrored polygon's vertices.

### Example

#### Input
```
2
2
4
1 1
3 1
3 3
1 3
3
2 2
4 2
4 4
2 4
```

#### Output
```
-1 1
1 1
1 3
-1 3
0 2
-2 2
-2 4
0 4
```

### Test Case Generator

```python
import random

def generate_point():
    return (random.randint(-10**3, 10**3), random.randint(-10**3, 10**3))

def generate_polygon(num_vertices):
    return [generate_point() for _ in range(num_vertices)]

def tcgen():
    M = random.randint(-10**3, 10**3)
    B = random.randint(1, 10)
    
    buildings = []
    for _ in range(B):
        V = random.randint(3, 10)  # Polygons have at least 3 vertices
        vertices = generate_polygon(V)
        buildings.append((V, vertices))
    
    return M, B, buildings

def format_input(M, B, buildings):
    input_str = f"{M}\n{B}\n"
    for V, vertices in buildings:
        input_str += f"{V}\n"
        for x, y in vertices:
            input_str += f"{x} {y}\n"
    return input_str.strip()

# Example Usage:
M, B, buildings = tcgen()
print(format_input(M, B, buildings))
```

### Explanation:
- The `tcgen` function generates a random test case.
- `generate_point` creates a random point within the range \([-10^3, 10^3]\).
- `generate_polygon` creates a polygon with a specified number of vertices.
- The `format_input` function formats the generated test case into the required input format for the problem.

Feel free to modify the ranges or constraints to better fit the actual problem statement if my assumptions were incorrect.