I played a lot of games on the C64, but this one probably held the record. It was a perennial favorite, and I was actually not too bad at it.
The title, Jumpman, could not be a better descriptor. You’re a little guy and you’re going to do a lot of jumping. Also running and climbing as you try to gather all the little orbs on a level. You’ll have to avoid robots, UFOs, evil jumpmen, and bullets that just float around waiting to kill you. Also falls, so many falls. The genius of Jumpman was that, crude as it was, there was sometimes a little scramble when he barely made a jump. That little bit of animation was enough to make one look at gaps and say “I’m pretty sure he can make that” and go for it.
Jumpman had 30 levels, I think, which got progressively harder. You could start at each group of ten, or you could do the grand tour. I am pretty sure I at least once completed the whole thing, but I can’t remember for certain.
I do know that I would sometimes play on the C64 in the morning before school and on at least one occasion missed the bus because I got further in Jumpman than I had before and there was no save game.
There was also Jumpman Jr, a lite version of the game which I had and played some of, but it was the original that got the most attention. Also, in the early 90s, a game called Jetpack, which owed a fair amount to Jumpman, got some plays on my computer. Jumpman was still the first and best for me, though.