I'm glad that's over. I ran through most of the levels quickly. 18, 23 and 25 were the difficult ones, and for some reason I ran into a perceptual barrier at level 25 that took a while to break through. The bombs were nothing more than a nuisance, serving as a another kind of opaque object. I would have liked another live element such as a diffraction grating that 'splits' a beam into invisible counterparts (that can be reflected but not light up a bullb) until they are rejoined.