Mechanism of Electromagnetic Interaction
The uninfluenced light speed c = dx/dt = |v|; these are all scalar speeds without direction as rotations or circulations, not linear displacement, which always has a direction.
Speed as the magnitude of velocity |v| = dx/dt → |v|*dt = dx. Substitute this in the speed equation for dx → (|v|*d)t/dt = |v|. Absolute speed is always greater than 0, since |v|=0 would be a privileged frame, which doesn't exist. Since units are arbitrary, any speed > 0 is equivalent to speed > 1 in some units, and that product |v|*dt is always greater than dt since |v| has been made > 1.
Consider the interaction of an electron having positive dx/dt and a positron having negative values as -dx/-dt consistent with the Feynman view. When aligned in constructive interference of superposition consider N electrons having dx/dt → N * (dx/dt) = (N*dx)/dt. By specification of an electron having positive dx, dt, and N>0, N*dx > dx. A greater dx means a larger distance. A larger distance in the same duration is a greater speed. Distance is measured from the center of mass (CM) of each object. A greater distance is a greater separation is observed as a Repulsive continuous separation of the objects. This is the mechanism of EM repulsion.
Now consider N electrons interacting with M positrons in constructive interference of superposition. We have N*dx/dt + M*(-dx/-dt), where N and M are positive integer counts. N*dx - M*dx < N*dx by definition of subtraction when M and dx are positive. (N-M)*(dx/dt) is a smaller distance in the same time. A smaller distance is observed as Attraction. This is a continuous Attractive reduction of distance at the CMs of the objects, and the mechanism for EM attraction.

