Certainly! Below is the test case generator for the problem "What Color Is The Universe?":

```python
import random

def tcgen():
    test_cases = []
    
    # Decide the number of test cases
    num_cases = random.randint(1, 10)  # You can adjust the number of test cases if needed

    for _ in range(num_cases):
        # Generate the size of array A
        A_size = random.randint(1, 1000000)
        
        # Generate the elements of array A
        A = [random.randint(1, 2**31 - 1) for _ in range(A_size)]
        
        # Append the test case to the list
        test_cases.append((A_size, A))
    
    # Add the terminating line "0"
    test_cases.append((0, []))
    
    return test_cases

# Function to print the test cases in the required format
def print_test_cases(test_cases):
    for size, arr in test_cases:
        if size == 0:
            print(0)
        else:
            print(size)
            print(" ".join(map(str, arr)))

# Generate and print the test cases
test_cases = tcgen()
print_test_cases(test_cases)
```

### Explanation:
1. **Test Case Generation**:
    - The number of test cases is randomly chosen between 1 and 10.
    - For each test case:
        - A random size for the array \( A \) is chosen between 1 and 1,000,000.
        - The elements of the array \( A \) are randomly chosen integers between 1 and \( 2^{31} - 1 \).
    - After generating the required number of test cases, a terminating line containing `0` is appended to the list of test cases.

2. **Printing Test Cases**:
    - The function `print_test_cases` iterates over each test case and prints it in the required format.
    - When it encounters the terminating case `(0, [])`, it prints `0`.

This generator will create a variety of test cases, including the edge case of having no elements in the array and terminating the input sequence correctly.