function doWave(g, x, y)
  checkCell(g, x+1, y, g[x][y].len + 1)
  checkCell(g, x-1, y, g[x][y].len + 1)
  checkCell(g, x, y+1, g[x][y].len + 1)
  checkCell(g, x, y-1, g[x][y].len + 1)

  doWave(g, x+1,y)
  doWave(g, x-1,y)
  doWave(g, x,y+1)
  doWave(g, x,y-1)
end

function checkCell(g, x, y, len)
  if x < 1 then return end
  if x > gridSize then return end
  if y < 1 then return end
  if y > gridSize then return end

  if g[x][y].type == TYPE_SEARCHED then return end
  if g[x][y].type == TYPE_SOLID then return end

  g[x][y].type = TYPE_SEARCHED
  g[x][y].len = len
end