Pretty fun platformer. The jump felt floaty but I found that worked well with the big open space ‘round the start of the level. It was fun to soar over all that. It didn’t feel very good in the narrower parts, though. Would be worth looking into how to make a jump feel less floaty. (I know I for one gotta do that next time I program a platformer; the last one I made had an sort of awful jump.)
I quite liked the BGM and the way the music changes when the timer activates. The rush back to the start actually felt quite tense. Put me in mind of a Metroid escape sequence.
Good work overall!