static Cell Cast(Cell[,] grid, int x, int y, int dX, int dY)
{
var shape = grid.Shape();
x += dX;
y += dY;
while ((x, y).WithinRect(shape))
{
var c = grid[x, y];
if (c != Cell.FLOOR)
{
return(c);
}
x += dX;
y += dY;
}
return(Cell.FLOOR);
}
