In the single mode game, the player controls Marty McFly through various stages set in 1955 in which he collects various clock icons in order to advance to the next level, and avoid the gradual vanishing of his future (indicated by a fading photograph at the bottom of the screen.) If the photograph fades fully, Marty would lose a life as it would show him vanishing. Collecting 100 clocks restored the photograph to its full, unfaded status. Two power-ups can help improve Marty's control: bowling balls that can destroy enemies and a skateboard which can speed up gameplay. There are also three minigames at the end of each stage, featuring such scenarios as Marty repelling Biff Tannen's gang of bullies from a cafe, blocking all the kisses Lorraine sends Marty (in the shape of little hearts), and having to position his guitar properly to stay in tune at the dance in order for George and Lorraine to kiss. The gameplay on these stages is often compared to that of Paperboy.
In the final stage, Marty gets to control the DeLorean time machine on the street at night, dodging lightning bolts and obstacles while accelerating in such a way as to reach 88 miles per hour precisely at the end of the stage, enabling the time machine to bring Marty home to 1985.
The game only contains two songs. One is a sped up version of Power of Love which plays throughout most of the game and Johnny B. Goode which plays in the guitar level.
If Marty loses all his lives, there would be a losing screen shot which reads "Tough luck Marty! It looks like you are stuck here". The player would also be shown that screen shot if Marty failed to get the DeLorean to 88 mph by the time he reached the wires, regardless of how many lives he had left. The game typically takes 35 to 50 minutes to complete.
Source: Wikipedia, "http://en.wikipedia.org/wiki/Back_to_the_Future_(video_game)," available under the CC-BY-SA License.