I'd advise you to start by building a barebones version of the game first, using placeholders and sketches. This will allow you to quickly test if a puzzle works and is fun, and you can get a basic playthrough of your entire game up and running very quickly. Then afterwards all you have to do is fill it up with graphics and animations. This approach also makes making changes to the design easier, as you won't have to redraw an entire room or all the walkcycles if you decide to change something.