Thanks, but your solution needs 4 tiles per frame and (even more critical) 2 sprites per enemy, when the invaders are bigger than 8 pixels.
There are already 4 enemies active at time + 2 bullets (4 with multiplexing) and 2 sprites for the main ship, so I cannot spend extra sprites for zooming enemies.
Actually I was thinking about a less demanding solution, using these attributes
CONST DOUBLEY = $0080 ' Make a double height sprite (with 2 GRAM cards).
CONST ZOOMY4 = $0200 ' Make the sprite quadruple (x4) the normal height.
CONST ZOOMX2 = $0400 ' Make the sprite twice the width.
In this way I could use 1 sprite and 2 gram tiles but with a reduced X resolution.
Anyway, even as it is now, a lot depends on the shape of the enemies one chooses.
Some scale better than others. I've removed some that look very bad replacing them with other shapes.
Look at them animated and tell what you think
In case I could change some of them or try to use the above options to increase the Y resolution.
Edited by artrag, Tue Apr 10, 2018 11:09 AM.