I personally do not recommend this program to anyone because of much smaller (and faster) ASM alternatives and even some much smaller BASIC alternatives, but this program is a prime example of how much speed you can gain in BASIC by sacrifying all the memory you can.
Instead of simply doing For(C,0,94:For(D,0,62:Pxl-Change(D,C:End:End, which is CONSIDERABLY smaller, the programmer has decided to just use one single For( loop and have one Pxl-Test( command for every pixel in the column number contained in the For( loop variable. In addition to this, he inverts two columns at once every loop, one on the left side and the other on the right side, until it reaches the center of the screen. The result: a whooping 1499 bytes of code just to do one thing that could have been done in about 14 bytes of code: invert the graph screen. But here's the thing: TI-BASIC For( loops are so slow to process that if he used the conventional 14 bytes method to do what he wanted, his program would run about twice slower. Had Netham inverted more pixels per For( loops than he did, his program would even have ran slightly faster. It's as pathetic as BASIC can get, sometimes: in cases where many things have to be displayed on screen in one loop, memory has to be sacrified to keep the program or game running at a decent speed.
Maybe the speed sacrifice in this program was too rash, since people will most likely not want a screen inverter this large on their calc, but I think if this method was used in a game where several enemies has to be displayed at once on the screen, their position/health being stored inside a list, like Galaxian, Space Invaders or a Warcraft, it would improve their speed a lot
Anyway, on the scoring of this screen inverter I would give:
Speed: 10/10 (for a BASIC program)
Overall: 5/10 only download if you want something fast, but no ASM, and don't care about speed.