Pong is controlled by holding the fire button and moving up/down.
Pac Man is initially quite confusing so read the docs within the download!
Space Invaders is easy, left/right moves and pushing up/down fires the gun.
The controls are odd and things get weird when all running everything at once! However, there's only so much my tiny brain could cope with and I found that I could play two games at once. I had no chance with three! Visually, it kinda works well but if you're struggling then you can alter each game's appearance using the numeric pad. Also, there's an option to invert colours which makes everything look ugly but it's much better on the eyes.
I think Andrei was one crazy, mixed-up kid who had a good laugh when coding this. Don't take it too seriously and practice with the controls because Video Games 1 is ridiculously entertaining. You will love it.