Very well polished game. The tutorial was really needed for me, and I still didn't get everything. Please add the option to go back in the explanations!
I also wondered whether I encountered a bug. Maybe I just didn't understand something, but given that I had an extra that was supposed to give more points for four colors, I was not expecting to get less when adding the fourth color (see screenshots).


The rules for the boss fight were also not very transparent to me.
The audio got on my nerves to be honest. The graphics are very stylish pixel retro charm, but for me a bit too pixelated, maybe. But it's a matter of taste.
In total, a nicely designed and smooth game, congratulations!