After it had constantly crashed on the instructions screen, I established that my Cambridge Computing Intelligent Joystick was not compatible with the program.
It was a relief to finally see the Giant Centipede rattling its way through the mushroom forest. With the offending unit unhitched, loading was error-free.
After selecting keyboard, or Mikro-Gen joystick, instructions alternated with scoring until the game is starred by choosing one or two players. The player moves to and fro, halfway up and down, shooting mushrooms and the centipede, with the score kept bottom left.
A spider bounces around placing more mushrooms, helped by a bug - both attempting to eat the player. If the centipede is removed all colours change and a new centipede appears.
Graphics, colour and movement are pleasingly simple and the response to the keys very good - though no user defined keys as the insert promises. Each animal has its own sound when moving and when killed. I found it simple, pleasing and addictive!