Anything you put on the battle map (on the token layer at least) is visible to all, so you can definitely make interactive puzzles. It's hard to give specifics on how to do it, because every puzzle will be different. There might be limits on what you can achieve without Pro subscription, because the scripting you get at that level enables a lot of automation. But IMO tabletop rpgs are not video games, and too much automation can be dangerous to the gameplay experience. Players should be interacting with each other and the GM, not the game itself. At the free subscriber level, you dont have to worry about that, because automation doesnt really exist. So you can set up puzzles with moving parts, hide parts of it on the GM layer, and when the players tell you how they interact with the puzzle, you can manipulate the parts behind the scene to change what they see on the board. That's pretty much how it should work for a tabletop rpg, and you can do things in roll20 this way that are hard to pull off at a physical table (changing the visible map on the fly, for instance). Hope this helps. Ask about specific details, and we can help.
