really really good just add a difficulty setting for people who suck like me

It's an interesting original game, I don't recall seeing anything like it before, or at least anytime recently. For a first (Unity) game, I think it's awesome.

There's a lot of useless unused space on the right (since you only move up and down), you could move the red line slightly to the right. The difficulty also stays the same during your entire playthrough; I'd consider starting slow and gradually increasing the speed (to a fixed max limit). Or gradually moving the red line to the left, if it starts e.g. in the middle.
I was about to say sometimes there's no time to dodge the blocks if there's a lot of them coming in a vertical line, but it's perfectly possible if I speed up using Shift (and I love the added detail of not being able to touch the walls).
It's also generally a good idea not to restart the song when you restart a level (keep playing it with an 'audio manager' which doesn't get destroyed):
https://docs.unity3d.com/ScriptReference/Object.DontDestroyOnLoad.html
Although this background music is pretty monotonous so it isn't as apparent.

This game is all about the high score, too, so you could also consider adding a scoreboard (build-in in Newgrounds), so players can compete with each other. More here: https://www.newgrounds.io/
Medals and scoreboards usually attract more players.

Good luck with your future games!