Thank you for alerting me to that, it will save me a lot of embarrassment and colour-counting by hand. I used a transparency tool in an earlier incarnation of it (which is how I had 15 colours) but I guess I didn't save that or reverted the changes. I hadn't realized what was meant by actual transparency (i.e. having a fully transparent background or section). It's fine, I learned something :)
The PJ Checker says there's no transparency; also, this is 8 colours. Also, transparency should be the background, given that the challenge calls for a sprite.
It must have been difficult at this siez, but the animation is very well done!