Font was a problem for me, as well. I'll have to look into some 4x8 fonts. Once I realized the font I was using wouldn't size down and still look good, I just wrote all the text I needed by hand in Pyxel :).
This game starts out really slow, but I am also a huge fan of these kinds of games. The difficulty got to me before I got to the end, though. I started getting a hang of the combo system towards the end. The diagonal matching really mixes up the formula I'm used to with other games (puyopuyo comes to mind).
The only critique I can give you is to maybe play a bit with mixing up the music a bit. The loop was a little short, so it started to get a little old after a while (to clarify, the song is actually very fitting -- I just wish it had a little more to keep it fresh for longer)
I really enjoyed this entry! Great work all around.