This is a decent take on the theme, I did like the momentum mechanic you've got with changing sizes while midair. The level design and platforming challenges could use some work though, I feel like falling into pits should just kill the player or otherwise punish them, just pressing R to restart felt a bit clunky. Furthermore, there is a lack of game juice and feel with any of the player's movements. Try adding sound effects, particles, movement acceleration/deceleration, and maybe even screenshake in some cases. There's a lot of little details that you can mess around with to really make the game pop! Nicely done though :)