What kind of game was the first video game

First of all, Pong is not the first video game ever. The earliest "computer game" was a missile simulator that was played on a cathode ray tube which used analog circuitry, not digital, to control the CRT beam and position a dot on the screen. Screen overlays were used for targets since graphics could not be drawn at the time.
The first computer game was a chess program that solved "mate-in-two" problems and was not powerful enough to play a full game.

After that it was a game called "Nim" which was played on a purpose built machine which weighed over a ton

however, In 1952, Alexander S. Douglas made the first computer game to use a digital graphical display. OXO, also known as Noughts and Crosses, is a version of tic-tac-toe for the Electronic Delay Storage Automatic Calculator (EDSAC) computer at the University of Cambridge. It was designed for the world's first stored-program computer, and used a rotary telephone controller for game control. There is a description of another "fun" program for EDSAC.