Hi André, thanks a lot for the feedback! Outlines for the bridge pieces sounds like a good idea - currently the pieces get bigger when they can be placed and are red tinted when they can't, but using outlines would definitely be neater and more consistent.
Allowing movement while placing the pieces would mean rethinking the control scheme, but you're right that it disrupts the gameplay currently. Changing that, and making the pieces easier to place, are probably going to be the highest priorities.
Thanks again for the feedback :D