In The Halley Project, the player assumes the role of a star pilot whose mission is to travel between the various bodies of the solar system. The game opens with a mix of electric guitar music and actual digitized speech — a considerable feat considering the limitations of the Apple II — during which the player is shown the text of a transmission sent from the headquarters of a body known as "P.L.A.N.E.T.":
You have been chosen from all the pilots in the Solar System to attempt to qualify for The Halley Project team. If you do indeed qualify, you will be invited to take part in the greatest scientific adventure in history: The Halley Project ... the Final Challenge.
Good luck, you will need it.
Neal "Buzz" Collins
Starbird 1st Class
The player starts out from a base on Halley's Comet and must first make his way to Earth, and then back to Halley. As longer and more difficult missions are completed, the player's rank increases from the starting level of Raven through Shrike, Vulture, Darter, Condor, Swift, Nighthawk, Falcon, Eagle, and finally Starbird.
A secret mission at the end of the game is accessible by typing in a password mailed by the software company after the player completes the last registered mission and receives a number code. The code is then mailed to "Project Halley" (in reality the software company that designed the game) on a pre-packaged postcard. A letter is then received from the software company instructing the player to load the program, go to Earth, and type MINDSCAPE to access the secret mission.
Source: Wikipedia, "The Halley Project", available under the CC-BY-SA License.