Some of the bricks are discolored. Try grabbing these!
I'm thinking about making these bricks a bit more obvious in a future update.
I have noticed them - they are obvious enough already.
Better make the grabbing/scrolling feature itself a bit more obvious, because when you hover your mouse over something you can click - you hear a sound, but grabbing/scrolling doesn't have that.
I had the same thing with the cannons in the night dome - figured that they are moved by scrolling after several attempts to move them while grabbing the "lever" or what was that.
If you are talking about the one with the loop symbol, then there is a hidden button on the second room in A2. There's one last mushroom minigame there which is a nightmare to complete so I'll just post the solution here if you don't want to do it right away (Although you will have to, cause there's another hidden room to get in A1 that leads to a treasure that can only be unlocked by succeed the mushroom challenge)
Loop symbole is : Green - Pink - Cyan - Pink - Cyan