Solution: Shuffled 2D Mazes

require 'grid'
require 'recursive_backtracker'
BACKGROUND = ChunkyPNG::Color::WHITE
WALL = ChunkyPNG::Color::BLACK
COLORS = %w( black gray red orange green blue lightblue purple )
  .map { |name| ChunkyPNG::Color(name) }
def shuffle_render(grid, cell_size: 60, gap: 10)
  img_width = cell_size * (grid.columns + 1) + gap * 2
  img_height = cell_size * grid.rows + gap * (grid.rows + 1)
  img = ChunkyPNG::Image.new(img_width + 1, img_height + 1, BACKGROUND)
  # shuffle the row positions; positions[i] tells the actual vertical
  # position of row i.
  positions = (0...grid.rows).to_a.shuffle
  colors = COLORS.shuffle
  grid.rows.times do |row|
    y = gap + positions[row] * (cell_size + gap)
    # big circle on the left showing the color of this row
    color = colors[positions[row]]
    img.circle(gap + cell_size / 2, y + cell_size / 2, cell_size * 0.3, color, color)
    # the rectangle outlining this row
    img.rect(gap + cell_size, y, gap + cell_size * (grid.columns + 1), y + cell_size, WALL, BACKGROUND)
    grid.columns.times do |col|
      x = gap + (col + 1) * cell_size
      cell = grid[row, col]
      x0 = x + cell_size * 0.5
      y0 = y + cell_size * 0.25
      r = cell_size * 0.1
      # draw a wall to the east if the cell isn't linked to its eastern
      # neighbor
      if cell.east && !cell.linked?(cell.east)
        img.line(x + cell_size, y+1, x + cell_size, y + cell_size-1, WALL)
      end
      if cell.linked?(cell.north)
        target = colors[positions[cell.north.row]]
        img.circle(x0, y0, r, target, target)
        y0 += cell_size * 0.5
      end
      if cell.linked?(cell.south)
        target = colors[positions[cell.south.row]]
        img.circle(x0, y0, r, target, target)
      end
    end
  end
  img
end
grid = Grid.new(5, 5)
RecursiveBacktracker.on(grid)
img = shuffle_render(grid)
img.save("/usercode/output/"+'1.png')
grid.to_png.save("/usercode/output/"+'2.png')