Great feedback! Thanks for coming back with more :)
Yeah, I think I'd want to add a longer indicator trail for blue slimes. Or perhaps a different animation for the selected slimes. The indicators were meant to help with remembering which slimes you had selected, but you're totally right about the blue ones.
My current plan is to try to make 100+ levels with these slimes, then introduce more colors with unique mechanics, do levels with 4 colors, then introduce yet another color and do levels with the original 3 plus the new one. I think more than 4 would make the puzzles a little too much.
I like the idea of having worlds built around a mechanical theme instead of just the slimes.
Thanks for all the wonderful feedbck