2600 Vanguard..bug or Eegg?

[alienblue]

Here's one that's never been

answered to my staisfaction. Five

times out of ten, when I play

VANGUARD on the 2600, in the second

"city" level (where you can choose

to go left or right) the first and

only E energy capsule will flip back

and forth (sorta like 3E)...has anyone else seen this? if so is it

a bug or easter egg?

 

[Tempest]

I'd say that's a bug. There are a few places in Vanguard where you can get weird stuff like that to happen. Generally when programmers put in an Easter Egg its pretty obvious.

 

Tempest

[StanJr]

I agree with Tempest, sounds like a bug, I've never seen or heard of that in any copy of Vanguard I have ever had. Vanguard is riddled with all kinds of bugs like that.

[Nostalgic]

I've seen this before. It probably is a bug - rather, an omission. The programmers probably didn't expect that a player would leave the energy capsule alone and face the aliens that flip back and forth.

 

There are two registers, REFP0 and REFP1, that if you write an 8 to them, will cause the corresponding sprite to be horizontally flipped. My guess is that if you choose the side with the aliens, the reflect register gets activated for the entire screen and is not switched back before the E gets displayed. Thus, it flips back and forth along with the aliens.