Simple and easy to play! I was a little confused about the goal of the game- is there a surface I reach if I jump efficiently enough and use my time well? Also adding some visuals or text to let me know what depth i'm at would be cool. Also scaling jump height with how long I hold the jump button would be super nice. Overall cool game!

Simple but cool idea. Would be nice to have background music or some sort of ambience as it feels quite empty.

Simple base for a platformer game. Some points of feedback I would say are adding variable jump height so how high you go depends on how long you hold up for. Also making the player stick to the floor when moving on slanted platforms would probably be a good idea here since you move horizontally faster than you fall making you unable to jump if you happen to press left or right slightly before jumping. (it's a setting in the characterbody node) Also if it's not implemented coyote time and buffer jumping helps platformers feel a lot better to play.

very good i liked it

It’s a good start for a platformer, but feels very incomplete.

Two simple-ish things I would change are the color of the time bar (blue on black, very hard to distinguish!), and make jumps cut off when you release the button so it’s not exactly the same curve each time.

Simple and effective! I'd love to see some fun mechanics built around this.
Bonus points if you can finish the game while holding your own breath! 
Good job !