I saw a lot of SLI and mixed modes. I'm guessing the helix animation was done with sprites (full screen height). But there are a lot of things that just seemed beyond what's possible on that platform. No idea how the Coca-cola logo was done (sprites moving together? but how the curves?), or how any of this was so smooth and fluid. Simply mind-blowing.. especially on a 2600, which IIRC have less capabilities than even a XL/XE (POKEY/ANTIC/etc).
The 2600 had a 1D display buffer. You would rewrite the contents of that buffer at the end of every scanline to actually get a 2D image. Game logic would usually only run during flyback.
(Yes, that's why atari chess did not show the board while thinking, and why if there was a bug you'd get a 1D horizontal image all over the screen)
