Thanks for checking out our game (and for sticking with it while being confused :))! Yeah the controls could use some work. I think one of our last minute balancing changes might've messed with the grabbing window, so thank you for bringing that up.
I completely forgot about adding in-game explanations for the mechanics, but essentially, some of the blocks are bad and will explode to disrupt your structure. Also if blocks fall off the conveyor belt they'll blow up too from the impact.
Thanks again for checking it out! Your game looks really fun, so I'll make sure to check it out myself when I have time :)