Hey! Nice start! I have a few notes.
The first thing I noticed were the sounds, They're a little repetitive. A simple way to fix this is to add a bit of variation in pitch and speed/tempo. Unity makes it pretty simple to do this, iirc.
Try making the spikes a bit more striking, and the background a bit less striking. I immediately though of red for the spikes (since red=bad, and also contrasts with the background more.) and dulling down/ reducing the contrast of the background a bit.
Sometimes the character seems to get caught on 'invisible walls.' Backing up and trying to walk forward again fixes this (usually), but it's still worth looking into.
Wall jumping feels a bit weird. I honestly don't know what it is. It might be the block character not being expressive enough to show when it's actually clinging to the wall. Or I might be wrong on that.
Am I supposed to be able to wall jump up a single wall? Because I can. Hug one wall and spam jump. To skip over the obstacles, just make sure you jump high enough to reach the bottom of the wall above it.
The character could be a bit more satisfying to move. Try making it a bit more reactive, like having it squish a bit when it lands, or having it shift some of its weight towards the direction it's moving in (If that's at all possible with this art style.) Maybe a have a little trail behind it? Or have the camera shift slightly to follow the characters movements? Maybe even put a goofy face on him that changes when things happen. (Jumping, moving, standing still, dying, moving to the next level, etc.)
Overall, pretty fun. Good luck! :)