"Up'N Down" (Sega 1983) - YouTube Video
https://www.youtube.com/watch?v=O9SK2aDgQxY
I just watched this on YouTube. The person said that this was contested at maximum difficulty.
If real, then this player is light-years ahead of what I can accomplish as he both (A) cleared loop 1 on a single life, never mind reaching stage 20, and (B) at this difficulty he got WAY past wave 7, the furthest that I have reached.
The video looks good for the MOST part but I spotted a few things here and there, the most glaring of which was within the 18:04-18:08 range. Between the momentum of the vehicle and the direction that it was going towards, I'm not 100% sure that this small sequence is even do-able. I'm going to ask two UND players that I know to check it out.
In any event what I did see that is VERY tough to do are the close-quarter jumps over flags that this gamer was pulling off consistently. This is extremely hard to do.
What I did NOT see, however, is what makes me wonder the most...when I play at this level of difficulty, the slightest pause in a spot results in cars racing towards me from behind. I did not see that for the most part here in cases where progression showed to a near-halt or complete halt. Additionally, in stage 6, the blue racing cars at this difficulty move way faster than you at the very onset of the stage, so much so that I sometimes cannot even get off a single jump.
This is clearly a better player than I am, but the maximum difficulty they claim in this video plays differently in some respects to what I experience on MAME...otherwise this player can wipe the floor with my score should they ever choose to do so.