If you had made this game a few years ago, you would have changed the history of video games. Very Good Luck!
Not me but if Philips had put more effort on Odyssey 2, it would stand better against the competitors.
I just noticed, that we have already a great Space Invaders sprite. I found it in Mage 3 (see Pic1). Just turn around and cut off the legs (Pic2)...
This is a nice sprite, but was not made by the chars, I'm using the sprites for 3 shields and the player missile. I need to use chars because there are only 4 sprites to use, not enough to build a screen full of enemies.
In the original Taito Space Invaders the invaders move one at a time per frame, that is also why the game speeds up as you shoot out an invader. The Taito Space Invader screen memory is bitmapped in vertical(!) stripes of 8 pixels. To move graphic data up or down a hardware 'barrel shifter' was used.
Yeah, I noticed that, I think the code is much poorly optimized in original, even using a slow processor, I think it could handle more aliens every frame. I will try to reproduce the original timing, but you need remember there will be 8 aliens per row instead 11, so I think the timing should be faster than the arcade, when the game starts.
You should finish your S.I. for G7400, it could be a nice addiction to it's game library.