Hopefully you are using the 7800 joypads or a third party joystick to play those games. Those original 7800 joysticks are painful on the hands!
Chris
Nope... converted some Radica sticks a few years back...
(It's funny, my son is 5 there and he's 9 now so he just got a kick seeing this picture again.)
Here's the original AtariAge page from that time...
http://www.atariage.com/forums/topic/72198-radica-space-invaders->-7800-joystick/
Great stick to play 7800 and 2600 games.
