Ha, I'm delighted to see someone actually make a game about refactoring. I have to say, though, the blocks being different colors really threw me off - I was trying to match colors the entire time my first try until I realized it was probably more like Tetris. As far as being minimal, keeping all the blocks the same color would make a lot of sense and also make the game more understandable. Another thing that would help is to make sure the player gets a successful line-clear early on, so they know what they're going for. I wasn't really sure what "success" would like look at first, and I ended up guessing wrong. If you have time, it might be worth prototyping a version of this where blocks disappear when four or more of the same color are touching.