"concrete feedback" right here.
First I played 40 AGBIC games today and this was one of my personal tops. So well done on this part. The idea carries the whole game but also the potencial to speedrun (the elevator level can be solved only by shooting yourself into the air). Let us come to the feedback
First of course make your site here pretty and add a GIF as a cover. This is one of these games that you can scroll though on twitter and understand at first sight. Perfect
Second change the graphics of course! I would go into the direction of looking cute with a animated face that changes with velocity and height. For some inspiration
Lastly there should be some UI and for a full game some (optinal) timer for people searching for highscores. I really enjoyed it and thank you for making it