So.....
Is the manual for the 7800 incorrect?
"when the difficulty switch is moved to the left the game becomes more difficult"
I pop in my space invaders cart and fire it up. I click the diff switch to the right and my laser cannon becomes larger. I click it to the left , it's smaller.
Here is a quote from the Space Invaders manual:
"The difficulty switches control the size of the laser cannons on the screen. In the b position, the cannon is smaller, and therefore easier for the beginning player to use. In the a position, the cannon is twice as large, and therefore more susceptible to enemy fire."
Which tells me that the switch on my 7800 is B left / A right