```ruby
class Grid
  SUBGRID_DIMENSIONS = [(0..2),(3..5),(6..8)].product([(0..2),(3..5),(6..8)])
  WIDTH = 9
  HEIGHT = 9

  delegate :size, to: :values

  def initialize(values, initial_grid: false)
    fail "impossibru grid construction detected" if values.count != grid_size

    convert_to_cells(values)
    lock_filled_cells if initial_grid
    break_cells_into_rows
  end

  def grid_size
    WIDTH * HEIGHT
  end

  def values
    @cells.flatten
  end

  def rows
    @cells
  end

  def columns
    @cells.transpose
  end

  def subgrids
    SUBGRID_DIMENSIONS.map do |row_range, column_range|
      @cells.slice(row_range).transpose.slice(column_range).flatten
    end
  end

  def complete?
    @cells.flatten.none?(&:empty?)
  end

  protected

  def convert_to_cells(values)
    @cells = values.map { |value| Cell.new(value) }
  end

  def lock_filled_cells
    @cells.reject(&:empty?).each(&:lock_cell)
  end

  def break_cells_into_rows
    @cells = @cells.each_slice(WIDTH).to_a
  end
end
```

Refactor columns to resolve using rows concept
user
```ruby
class Grid
  SUBGRID_DIMENSIONS = [(0..2),(3..5),(6..8)].product([(0..2),(3..5),(6..8)])
  WIDTH = 9
  HEIGHT = 9

  delegate :size, to: :values

  def initialize(values, initial_grid: false)
    fail "impossibru grid construction detected" if values.count != grid_size

    convert_to_cells(values)
    lock_filled_cells if initial_grid
    break_cells_into_rows
  end

  def grid_size
    WIDTH * HEIGHT
  end

  def values
    @cells.flatten
  end

  def rows
    @cells
  end

  def columns
    rows.transpose
  end

  def subgrids
    SUBGRID_DIMENSIONS.map do |row_range, column_range|
      @cells.slice(row_range).transpose.slice(column_range).flatten
    end
  end

  def complete?
    @cells.flatten.none?(&:empty?)
  end

  protected

  def convert_to_cells(values)
    @cells = values.map { |value| Cell.new(value) }
  end

  def lock_filled_cells
    @cells.reject(&:empty?).each(&:lock_cell)
  end

  def break_cells_into_rows
    @cells = @cells.each_slice(WIDTH).to_a
  end
end
```
assistant