Scrolling with status bar demo

This old demo I did back in 2008.

It shows how to have a status bar on the top and scroll vertically the playfield that is below by writes to $2006.
A more recent version reduces the size of the status bar by taking advantage of the "fine-scroll" bits in the most significant bits of $2006.1

Another variant of this have the status bar at the bottom, and use an automatically modified tile in CHR-RAM (like Solar Jetman) to force a sprite zero hit.

The gap between the status bar and the playfield could be shrunk even further with a four-write sequence, as seen in this post by tokumaru.