The little symbol that appears on the title screen is actually the letters db (for Dick Balaska).
Starting on run 9, each run has a secret door with the initials db and cb (for the programmer's former wife, Cindy) on it. If you run up to the door, you’ll get about 1,000 points, but if you turn away after first seeing it, you won’t get any.
An addendum sheet was later included, which corrects some errors in the manual, since the game was changed prior to being released.
RAM PLUS inside.
To execute an emergency transport, hold FIRE and rotate the joystick in either direction during a run. Note: This may only be done once per run. This feature is not documented in the manual.