Yeah, there's 2 ways to resize an object. The safe way is holding the ctrl key and scrolling the wheel up or down. The not safe way is holding shift and scrolling the wheel. (it doesn't actually resize it, it puts it further, or closer to the screen, giving it the illusion of being bigger or smaller, and also causing it to scroll around parallax style)

For vertical thin blocks, hold shift and scroll the wheel (don't worry, with tiles it won't do anything creepy) until you get a horizontal strip, then hold ctrl and scroll the wheel to rotate it vertically. If it doesn't look right compared to other tiles, hold space and scroll the wheel to flip it until it does.

Thank you, this helps a lot.

Occasionally, my hazards will literally move across the screen, following the player, and the same will sometimes happen with Decorations.

I've been told this happens when you resize a hazard. If that's true, is there any way to safely resize a hazard/decoration?

Also, how do you get vertical thin blocks?

Thanks.