The design was brand new and not an evolution or tweak of an existing commercial circuit, but a new approach to overdriving an amplifier.
It has a complex power supply giving +18 -9 which increased the pedal’s headroom. This improved the slew rate of the op-amps used, which essentially is the time they take to react to an input signal. This means for the guitarist that the pedal becomes very responsive.
The circuitry also mixes a combination of overdriven and the original dry signal to great effect.
Also, part of the mystique is the clipping diodes used. These are the components that chop the top from the pure signal to give the overdriven sound. The Centaur uses germanium diodes.
Germanium components went out of favour for a time and have been largely replaced by silicon due to its greater resilience, apart from in some applications such as this. Again, this seems like the tubes versus solid-state amplifier debate. Whilst in theory yesterday’s technology, some guitarists prefer the sound of germanium clipping diodes to silicon.