I like the idea
Either I've missed it or there isn't a proper explanation of the various placeable objects. The basic function is obvious, but not the exact range, etc (maybe you could add a tutorial at the beginning?) I think the player should be able to decide when the little guy starts to move. I wasn't able to place objects while the guy is inside a cannon which would be a handy feature. The animation when he's shot out of the cannons is way too slow.
Otherwise it's a decent design, it's just the slow pace and the lack of music that make the experience a bit boring.