The idea is cool. You have to think carefully before placing anything or you get screwed up pretty quickly.
There are a coule of issues though. A way to restart the level manually would be nice. Also it's kinda hard to see where you're gonna place an object, some kind of preview (like half-transparent silhouette) would help. Sometimes Somni would get through a wall or fall of a bridge even though it seems to be placed correctly. Overall, these don't affect gameplay too much but may cause frustration sometimes.