Freedom Fighter scrolling technique article finally here!

Thanks for the explanation.
It looks like you have to design your tiles very carefully.
And thanks for explaining it so newbies like me can understand it

Thank you

My key learning is, that the 1 pixel line scrolling was done on the cost of reduced number of tiles. If I compare the tile sets between Freedom Fighter and Alien Attack, I ask myself if I could have accepted this limitation when I created the background graphics for AA.
Don't get me wrong here, its still amazing how you managed to draw backgrounds with this limited nunber of tiles. But as an artist I was happy to say: "ok, and now I put a sea monster here in this lake. Hmmm 6 tiles in size. Ok, no problem, still 27 left in the tile banks...".

Great read !
For me it is always interesting to see how somebody else solved the same problem as I did (the 1-pixel vertical scrolling in PAC-01). What striked me was to see how completely different our solutions are, probably caused by different starting points (you wanted to be able to shift to different tile sets; I was primarily focused on speed)
So actually the approach I used was to have a fixed tile set (so no changes in pattern and color tables during play) and only update the entire nametable each frame. This way I didn't need double buffering (but racing the beam...) I was able to squeeze the playfield into 29 different character transitions, which all needed 8 tiles. So I had 256-(29x8) = 24 non-scrolling characters left to draw the scoring board and green bits. In the top third of the screen I used them for the scores, in the middle third I had the catched ghosts, and in the bottom third the green bits.
Each game asks for a different approach and it is helpful to see and learn how somebody else does it !

Hi Micha! Yep, different solutions for different aims. Mine routine is able to different speed too. As it happens at the half level: to do it, is enough to change the offset increment. Infact my scrolling can do 1,2,4 and 8 pixels steps. Obviously ot is possible also using fixed tileset