Yertle who?
I have no clue what or who Yertle the Turtle is, but this game was actually quite fun. While it lasted. It's an interesting idea to have all those movement shifts and colour changes. The spontaneity of it was actually quite intriguing.
However, I do feel the difficulty progressed a little too fast and hence the play time of this game was very very low. It was over very fast mainly because you didn't quite stretch it out for what it was worth. Sure, you can sometimes stretch it a bit too much and then make something utterly boring, but this was on the other end of the scale. The progression was far too quick and before I knew it, it became too difficult to even maneuver properly.
You may not want to necessarily slow down every element in the game. For example, I think the rate at which the block directions change can remain, but the rate at which new colours are added is far too high. In a matter of seconds, I've got so many new colours on the screen that the colours I can collect are only 1 or 2 boxes. And by the time i maneuver my way to them, my own colour has changed.
The concept of this game is very sound. But it just moves by way to quick. It's rushed almost and I didn't get to enjoy it as much as I wanted to. Take the time to gradually introduce things. Don't have something new every five seconds or something. And that's especially once the difficulty gets harder. You might want to let that level of difficulty settle a little bit before moving onward.
Has great potential, but as of now, it's limited itself to barely a minute of fun.