Now part of this picture seems obvious. The animated Alien Syndrome
logo does not use the same color scheme as the rest and the background pieces
appear by scrolling beneath it. It also uses less than 4 colors (2 actually)
so my guess is that it is made of several multicolor sprites. The logo is
exactely 8 sprites wide (maximum a C64 can display at a time) and it is
taller than one sprite, so it looks like the multiplexor was used. I took
for granted that I could use a third color in the logo (white) for a better
volume effect. Hope that third color was not in use somewhere.
The background part is somewhat more complex. It is using multicolor character
mode. In this mode, you can choose two colors that can be used freely (colors 2 and 3)
anywhere on screen, and one additional color (color 1, also named main color)
that can be different on each 8X8 cell.
A color split has been used between the top part and the rest, as the color scheme
is visibly different. The left and middle right parts share the same colors
(except for main color, that is). After some investigation from Shaun (thanks), it
appears the bottom right part is made of sprites. That allows for a different set of
three colors in that part. I changed colors 2 and 3 in the top and bottom parts, which
Finally, The SEGA logo is probably a set of monochrome characters. I just made it
smaller, so that can't hurt.