I love this game, you have one simple mechanic and polished it! Having subtle tutorials in the background WITH VIDEO is really great for teaching a player quickly without spending much time on a tutorial. Time slowing down when you can make a second jump is a really great choice to let the player aim their new jump but still need to act quickly.
I found the game to be pretty challenging at first, especially dodging the attacks from the two second bosses, but I got used to it after a bit and using the right click to dodge.
Awesome job!