Great, I love the classic mode of the game, although I feel that from level 15 it becomes very difficult, and from level 20 it all depends on luck since you do not have time to think, in my best game I barely reached level 24 I don't remember how hard I put it, but I don't think I'm that bad at playing Tetris.
That is why I would recommend that they include a mode where you can limit the maximum speed of the game, it is not fun to be at the top and then start over.
Although if you allow me to dream, I think that a life system would be great, also a bar that fills when you make a piece fall faster and serves to briefly slow down the fall of other pieces, I am also the only one who would like to rescue some of the mechanics of the block games of the "Brick Games", for example that piece made up of a single block that you receive passes through everything until you fill a gap, this could be given as a bonus when completing a level.
Changing the subject, I don't understand what the "H.DROP" option is for, I assumed it was to retain pieces or something like that, but if that's what I don't know how to activate the option, does the logic of dropping pieces change or something like that?
On the other hand I think the soundtrack is great, although it is a shame that there is only one melody for the game.
Cheers, great game