One (or five) too many times slamming my fist into the keyboard/trackp
Anyway-- I figured that while I was fixing the problem, I might as well get a little funky. Ordered the black top case for my white MacBook. Why not? Easy-peasy installation. In and out in half an hour, maybe less.
Apple's design on this product is a bit flawed. Any but the gentlest closing of the lid (screen) onto the top case (keyboard) will cause the two small ridges on the lid to crack the top case where they meet it. Yes, those two, inch-long ridges located about an inch in from each side, and very near to the upper edge of the lid. My top case cracked (on the right side, not the left, oddly) not terribly long after I bought this Mac new, despite the fact that I was normally gentle with it. The damage manifested as a few millimeters of the top case surface breaking off along about two inches of the edge, just beneath the right-side lid ridge, exposing a narrow slot into the laptop innards, which I taped to keep clear of debris. (This issue is unrelated to my admitted violence to the keyboard which necessitated this repair-- just an observation about product design.)