The black blob is generally called a "chip on board" or COB, I believe.
and yeah, it's a cheap way to mass-produce something... and in some cases it also helps prevent reverse-engineering.
Anyway, making a top like that is definitely doable with a standard microcontroller, if you want some patterns to the lights. Years ago I did a school project where we made a persistence-of-vision toy somewhat like this using a PIC, where we made a wand you waved in the air and it would display messages.
I would guess that the thing in the tube is probably some sort of really simple rotation sensor; most likely, when the top spins, it causes the two contacts to close, activating the lights. A lot of the similar toys I've seen (yo-yos with lights, etc) use something as simple as a little weight on the end of a spring, which flexes outward when it spins. I doubt it would use mercury, that would be more hazardous for a toy kids would be likely to break, and also more expensive than a little spring or similar.