Thanks for your answer. :)
At this time I will only comment the "vertical bars". They are ladders :-D. […] I had to make tham as a "rocket-lift" instead :-D :-D :-D
Aaaah, all right! XD I was not that far thinking of ramps, then. ;)
Those are meant to be the workaround, if you are in short of available jumps, and sometimes the ladders are necessary too.
Ah, so this answers my question about being possibly stuck in a level! :)
So, my advice would be that there is some disadvantage when you take a ladder. For example, there is an enemy just above, or it takes longer while you have a countdown that forces you to finish the level under some time limit. :)