Super Circuit is an excellent game, no doubt-but one best played in short spurts.
The basic how-to of the game is simply to race around the many different tracks and try to place in first. Use items like shells to knock opponents out of the way, or get coins to speed ahead of them. You can choose from 8 different characters that each have their own special ups-and-downs.
The graphics are incredible for a portable system such as this. This is one of the few games that makes use of the GBA's 32-bit proccessor. The graphics are smooth and there's no slowdown at all. Sometimes, the graphics are more pixelated than they need to be, but it is hardly noticeable during the race.
Sound is good. There are voice clips from all the characters, and music is catchy to listen to.
The multiplayer is really good. You can play Single-Pak and Multi-Pak. In Single-Pak, everyone races as a different colored Yoshi on 4 tracks, and Multi-Pak mode lets you race in the GP, a simple race, or the coveted battle mode(you know, the balloons). It's really fun to play with friends.
I highly recommend this game to anyone! The only thing is, you get bored of it after a couple of races, so it's best played in short spurts.