Reactive Factory is the fourth level made available for play in Sonic R. It contains two Chaos Emeralds and collecting all five Sonic tokens will allow you to race against and unlock Metal Knuckles. The track has a machine that will give you rings at no cost, making these tasks easier.
Instruction Manual Description
||Here you are transported into the future! Enter the factory of tomorrow, a completely automated wonder. There is lots of room to run, but there are also many hidden surprises and traps. What appears to be at first a simple course is really the hardest of the four courses.