static char[,] ExpandProblem(char[,] arr)
{
Span2D <char> insert = new char[, ]
{
{ ' ', ' ', '#', 'D', '#', 'C', '#', 'B', '#', 'A', '#', ' ', ' ' },
{ ' ', ' ', '#', 'D', '#', 'B', '#', 'A', '#', 'C', '#', ' ', ' ' },
};
var span = arr.AsSpan2D();
var expanded = new char[span.Height + 2, span.Width];
var expandedSpan = expanded.AsSpan2D();
span[0..3, ..].CopyTo(expandedSpan[0..3, ..]);
static char[,] CombineTiles(Tile[,] puzzle)
{
var tileSize = puzzle[0, 0].Top.Length - 2;
var tileCount = puzzle.GetLength(0);
var imageSize = tileSize * tileCount;
var image = new char[imageSize, imageSize];
var span = image.AsSpan2D();
for (var row = 0; row < puzzle.GetLength(0); row++)
{
for (var column = 0; column < puzzle.GetLength(1); column++)
{
var rowStart = row * tileSize;
var colStart = column * tileSize;
var dest = span[rowStart..(rowStart + tileSize), colStart..(colStart + tileSize)];
static char[,] ApplyRules(char[,] input, RuleSet rules, int size)
{
var memory = input.AsMemory2D();
var panels = input.GetLength(0) / size;
var resultSize = size + 1;
var newSize = resultSize * panels;
var result = new char[newSize, newSize];
var resultSpan = result.AsSpan2D();
for (var y = 0; y < panels; y++)
{
var yOffset = y * size;
var resultYOffset = y * resultSize;
for (var x = 0; x < panels; x++)
{
var xOffset = x * size;
var resultXOffset = x * resultSize;
var target = resultSpan[resultXOffset..(resultXOffset + resultSize), resultYOffset..(resultYOffset + resultSize)];