A. Publicly Released Information
B. Generally Recognized Information
The "Super Solenoid Engine" is the Angels' source of limitless motive energy. It is thought that this gives the Angels abilities such as self-regeneration and metamorphosis that, for living creatures, exceed the bounds of common sense.
C. Confidential Information
The S² Engine Theory was advocated by Dr. Katsuragi. As the world is formed with spirals, the engine acquires energy from its shape, which is the same as DNA. From here, the S² Engine was being envisioned as an energy source that would attempt to procure helical energy — in other words, an inexhaustible supply.
D. In-Depth Information
The Fruit of Life. This is the one thing that an Eva requires in order to gain an existence equal to that of Adam.