What is there to say about echochrome? It's very straight forward and pretty much all descriptions available are quite accurate to what you'll get with the final product. Is it possible for a game to be so straight forward it does not feel rewarding, thus filling such a game with empty challenges? I think the answer is yes, though I'm not really certain. While I feel echochrome is a good game, something about it feels empty; and it's not the simple visuals.
There is a horde of puzzles to solve your way through and successfully completing one will unlock the next in line, but you're constantly doing the same thing with a steadily increasing difficulty and nothing more. And this begs the question of whether what echochrome is really constitutes a game. The concept is very appealing but its translation to gameplay will not satisfy everyone (obviously), while others will praise its minimalist style and art-game standing.
At no point did I ever feel compelled to set time aside to specifically play echochrome. It was generally something I would only start while waiting for something, and only then because it is just so damn intermittent. It's still hard to fault echochrome for these things because it succeeds at what it sets out to do. I just wish there was more satisfaction to be had.