This game has unused graphics.
Sky Raider is most likely the first ever vertically scrolling shooter, and it's at a rather unique perspective at that.
It's missing a sense of danger though, since the only real enemy is the game timer.
The initials H.J., F.H., M.N., and L.M. are hidden in the same ROM as the game's font. It's unknown who these people are: They're not the initials of the three people who worked on the game, and they don't match up with anyone known to work at Atari at the time. The identity of these four people might be lost to time.