Boo Baa Boor Baa. (That was the noise it made, by the way.)
Simon was a circular beepy pattern remembering game produced by MB. It had 4 brightly coloured sections with lights behind each of them.
If Simon lit up the red section, you had to press red.
Then it would light up red followed by yellow. So you had to press red then yellow.
Then red, yellow, red. And you copied it, repeating the pattern over and over again. The pattern became so horrendously long that you inevitably couldn’t remember it and accidentally pressed a wrong colour, ending your winning streak.
It also used to speed up the longer your game went on for, adding further pressure and stress.