This is a cool concept. I agree that it's a bit difficult to figure out what's going on at first. More explanation could help, but IMO what would be most helpful is a persistent display of the current block somewhere on screen to the side of the board. Might be cool to show the block that will come after that too, like Tetris.
FYI the Itch version doesn't work in Safari, though Chrome is fine. It's throwing a max call stack exceeded. I think I hit the same thing when deploying my game, and disabling gzip in the build resolved it. You know, in case you're concerned about the other 4 people using Safari :D