This was a pretty fun game once I got the hang of it, and the pixel art is definitely really great! One thing I would add is a little more explanation/details in the rules, like how it's possible to go diagonal or out of order and still make a combo. Also I didn't even know power-ups were possible or what they were, so I'd add something about that in the rules too.
The other note I have is that the timer comes off as impossibly fast at times, even after playing for a while and getting the hang of things. Maybe add an option in the future for different difficulty levels that tie into the timer speed. As of right now it feels sort of like being thrown directly into hard mode, which can be fun too, but can also turn a lot of people off especially because it's only first introductory stage. Still though, it's a pretty fun and challenging little game! The art and animations are great!