How to display isometric maps with pytmx?

[nilamo]

...and once I actually woke up, I realized all that math can be based entirely off the indices, instead of having temporary variables. And also, that the tiles needed to be rotated 45 degrees:

    def render(self, surface):
        ti = self.tmxdata.get_tile_image_by_gid
        for layer in self.tmxdata.visible_layers:
            if isinstance(layer, pytmx.TiledTileLayer):
                for x, y, gid, in layer:
                    x_offset = (WIDTH / 2) + (self.tmxdata.tilewidth / 2 * (x+1)) - (self.tmxdata.tilewidth / 2 * (y+1))
                    y_offset = ((y+1) * self.tmxdata.tileheight) + (self.tmxdata.tileheight * x)

                    tile = ti(gid)
                    if tile:
                        rotated = pg.transform.rotate(tile.convert_alpha(), 45)
                        surface.blit(rotated, (x_offset, y_offset))