Wow, solid gameplay here! It's simple, but I found it to be very intuitive and addictive! I easily found myself coming back over and over to play the endless mode and getting in an almost trance-like state of chaining. Again, it's basic, but something about it is just constructed well and satisfying to play, so kudos on that!
The only feedback I can think of is just minor stuff, like how I wish it taught the controls a bit more (I had no idea how to proceed on sprint mode for a while haha) and that I thought the gray blocks couldn't be chained at first due to their color making them seem 'inert'. Oh, and I did wish that the game gave some more feedback and different sounds for making combos bigger than 3 and such.
Oh, one more feedback! I did try to make a cool combo where I chained a horizontal row, and then tried to chain a horizontal row right on top of it during the blinking. Unfortunately, it didn't allow me to do this as technically I was making a chain on top of an unstable blinking platform (and once the blinking platform was gone, the left over wouldn't form the chain anymore since one block would fall through). So technically, the game was reading the future and correctly seeing that my chain was illegal and wouldn't hold up even though it did temporarily. But still, I felt a little let down that the game didn't let me do a cool trick like that. Maybe a case where the game was too smartly programmed to not allow it, haha. Oh well!