tile map view

public class TileMapView : GameState
{
    static readonly float[] ROTATIONS = {
        0f,
        MathHelper.PiOver2,
        MathHelper.Pi,
        MathHelper.PiOver2 * 3
    };

    public static ushort MakeTileID(int x, int y, SpriteEffects m = SpriteEffects.None, int r = 0)
    {
        return (ushort)(
            (x & 63) | ((y & 63) << 6) | ((r & 3) << 12) | ((int)m << 14)
            );
    }

    public TileMapView(GameStateMachine gsm, GraphicsDevice gd, ContentManager cm) : base(gsm)
    {
        spriteBatch = new SpriteBatch(gd);

        tileset = cm.Load<Texture2D>("proto-tileset");

        width = 24;
        height = 16;
        layers = new ushort[3, width, height];

        for (int x = 0; x < width; x++)
            for (int y = 0; y < height; y++)
            {
                layers[0, x, y] = MakeTileID(5, 18);
                layers[1, x, y] = layers[2, x, y] = 0xFFF;
            }

        for (int i = 3; i < 10; i++)
            layers[0, i + 4, i] = MakeTileID(3, 25);
        for (int i = 5; i < 11; i++)
            layers[0, i + 6, i] = MakeTileID(3, 25);
        for (int i = 4; i < 9; i++)
            layers[0, i + 8, i] = MakeTileID(3, 25);

        layers[1, 7, 9] = MakeTileID(1, 0, SpriteEffects.FlipHorizontally | SpriteEffects.FlipVertically, 2);
    }

    SpriteBatch spriteBatch;

    int width, height;
    Texture2D tileset;
    ushort[,,] layers;

    public override void Draw()
    {
        DrawLayer(0);
        DrawLayer(1);
        DrawLayer(2);
    }

    void DrawLayer(int layerIndex)
    {
        spriteBatch.Begin();

        Rectangle source = new Rectangle(0, 0, 16, 16);
        Rectangle destin = new Rectangle(0, 0, 16, 16);

        int rot = 0;

        Vector2 origin = new Vector2(8, 8);

        SpriteEffects mirroring = SpriteEffects.None;

        for (int x = 0; x < width; x++)
            for (int y = 0; y < height; y++)
            {
                destin.X = x * 16;
                destin.Y = y * 16;

                source.X = (layers[layerIndex, x, y] & 63) * 16;
                source.Y = ((layers[layerIndex, x, y] >> 6) & 63) * 16;

                mirroring = (SpriteEffects)((layers[layerIndex, x, y] >> 14) & 3);
                rot = (layers[layerIndex, x, y] >> 12) & 3;

                spriteBatch.Draw(tileset, destin, source, Color.White, ROTATIONS[rot], origin, mirroring, 0);
            }

        spriteBatch.End();
    }
}