Yes, i did heard about Cayote time as Celeste is my favourite game! :D But I didn't implement it because I thought "Welp, it's not that of a big feuture" but ohhh boyy... was I wrong! Coyote time makes a HUGE different and it's not that hard to implement, I need to keep that in mind next time i'll do a platformer, beucause I should've make the movement the top priority of this game!
Regarding the first level I totally forgot to put Checkpoints since it was one of the last things I implemented! And if I placed some of them in the first level I think it would be easier and fairer, it was tottaly my bad!
Thanks a lot for your kind feedback, all the critics help me a buch be a better developer! :D