public Day20()
{
Part = 2;
Key = InputLine.ToBitArray('#');
Game = new GameOfLife(true);
Game.Expanding = true;
Game.NeighborFunction = pos => pos.RectAround(1, 1);
Game.UpdateFunction = cell =>
{
var index = cell.Neighbors().BitsToInt();
return(Key[index]);
};
var input = AllGroups[1].Select2D(c => c == '#').ToGrid();
foreach (var(pos, value) in input)
{
Game[pos] = value;
}
}