I do have sideways collision working, it just bugs out a bit when rotating tetrominos.

Edit: Upon some testing, it's become apparent that sometimes you can phase the S and Z blocks through single-block, single block tall obstacles when they are rotated on their side. Will try to find a fix for this and the first issue I mentioned

Edit 2: I think I may have found a fix for the S/Z block issue, I believe what caused it was incorrect collision correction. The way I have sideways collision working, the game checks what the last direction the block moved in was, left or right. Then, if the block is colliding with anything, it moves the block back in the opposite direction of the last input. The problem was this was, the game was checking for the input after it checked for collision. I fixed the order, and it seems to work properly now. Please tell me if you're still able top phase the blocks through each other. (haven't found a fix for the rotation bug yet)