The Back to the Future movies were pretty straightforward, and were more silly than anything. The game based on parts 2 and 3 of the trilogy was not only not straightforward in the slightest, it was quite tough.
The only thing that these games had in common with the movies were that the characters were named the same things that they were in the movies, though they didn’t look very much like their namesakes, there was a time-traveling car that flew around, and you had to stop Biff and restore the timeline.
What you had to do was travel around the different times to find different object rooms in the city. These object rooms would have some kind of object to find and a challenge that you had to complete. The challenges were mind-bendingly difficult, and didn’t make any sense whatsoever. They were mostly the variety of collecting a set number of objects in a certain amount of time.
You travel through time to access different areas in the city. If a ledge is too high, you can plant an acorn in 1955 and climb a tree in 1985. If a gap is too large to jump in 1985, go back to 1955 where the street hasn’t eroded yet.
There are something like 50 of the ridiculous item rooms for you to find and complete, and doing so will reveal the answer to a puzzle that lets you access the second half of the game, which is apparently just like the first part except that you’re stuck in 1855 and you’re wearing a cowboy hat. I don’t really know that much about the second half of the game, I was only able to play through about half of the first half.