So good as usual. More fun than portal bridge constructor.
I spent a few mins trying to place blocks where I thought they should go initially.
IMO it's missing something at first to let the player know valid placement locations or to teach about putting blocks under instead of on top. (I guess technically you do have that with grey/bright but I missed it). Maybe let them place it anywhere but it falls? Maybe have the block show the spring thingy animating when you drag it or something? Maybe get rid of the icons entirely and just show the spring/etc with a border/cost and place where it should go?
The initial drag might block progress for some people too but I got that part pretty quickly.