[sdk77]

The oscilloscope works like a vector display (or x-y plotter). A circle can be displayed by feeding a sinewave voltage to the Y input and a cosine to the X input. Adding a voltage to the Y input moves the ball up and down. Similarly, adding a voltage to the X input moves the ball left to right. Increasing the amplitude of both the X and Y signal will enlarge the ball. State is maintained by flip-flops built from discrete transistors (mono-stable multivibrators). Collision detection is just a matter of comparing the X and Y voltage of object A to the X and Y voltage of object B. If the voltage are (almost) the same, both objects are on the same screen position.