Played a bit further, this time used the 'jump levels' which I hadn't spotted before as an option (maybe flag that in-game?), although struggling with the controls a bit, the later levels are especially fun / good design. I just found some of the early levels too frustrating/unforgiving originally. One small tweak I'd like is if on death the level reset to where it started, so I don't have to wait for things to get back to their 'ready for me to jump on the platform etc' state.