def tower_builder(n_floors):
    if n_floors == 0:
        return []
        
    count = 1
    result = []

    for i in range(1, n_floors + 1):
      stars = '*' * (2 * i - 1)
      space = ' ' * (n_floors - i)
      result.append(space + stars + space)            
    return result
    