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Congrats on your first game!

Some specific things about the controls (as others have already generally mentioned), you want to aim for them to feel intentional and snappy. Getting good platformer controls can take a lot of tweaking or prior knowledge. There feels like a slight lag from when the player presses the jump button to when they actually jump, and the momentum of the forward motion is continuing during this time, which would lead to me falling off the edge without ever jumping. This disconnect feels frustrating and like it's not my fault, but the game's fault (a game can be difficult/frustrating and still feel fair). You could consider giving a few frames of wiggle room after the player has left the platform to still register the jump. You can look into GMTK's own video on Celeste to get some other ideas.

Also I think it's quite common for space to be the jump button. You could have both w/z and the space button  be jump and leave it up to the preference of the player.

It's also worth considering the intention of the level design. The first level is fairly simple in design, but not simple to play though. The jumps between the platforms are difficult because of the low ceiling and the fast forward movement of the character, mixed with the low friction with the ground. If the intention is to teach the player about shrinking to get through the smaller corridor, then just do that, and just once.

Good game ideas though, which fit the theme nicely. I also liked the art and that you added a bit of story.