Better news: I have the part I'd been trying to invent for my robot for Embedded Systems all constructed, and unlike most Lego Mindstorms constructions I've invented, it shows signs of being inclined to not disintegrate. It's a wall-follower part: a gizmo to let the robot figure out how far it is from the left wall, so it can follow it reasonably. This involves a springloaded (okay, rubber-band-loaded) construction of six axles, including the one mounting the roll wheel (so it moves smoothly over the wall), the one acting as a bar that holds the one mounting the roll wheel with a T-connector on the end, the two holding the other end of the axle to make sure it slides back and forth rather than providing torque (no, not turq, the tendency to twist rather than slide), and finally an axle for it to slide over. A rubber band wrapped around the vertical axles and a half-pin cause the device to try to extend itself unless the robot is indeed against a wall.
Mounted on the elbow joint holding the second axle is a yellow Swiss 2x1 brick ("swiss", in this context, means it has a hole through it: reference to a variety of cheese), with a stack of a yellow 2x2, then a blue 2x2, then two black 2x2s stacked on top of it. All of these are lying sideways... right in front of a light sensor.
So by having the colors on the bar "fade" from dark to light, the light sensor reading gives a fairly reasonable estimate of how far the robot is from the left wall.
The construction is more complicated than that; I took several photos, which I'll upload later. I didn't take them to show off so much as to save the design for my own reference later!
And I saw a bunny outside earlier. It was cute. It was also unafraid of me, which is why I have several good pictures of it, too...
So despite the PDA failure, today turned out pretty good.