Super fun little game. 

But I wish that there was an alternative gamemode where instead of having a set amount of time, you just have to beat it as fast as you can, since I keep running out of time just as I get to the more fun part of the puzzle.

OMG!

This game has me in its grip.

Each game is a quick little challenge. So simple, but hard. I keep having to try one more time to break my record (currently 100). 

A neat thing, for when the short time limit gets frustrating, is that you can keep going. The time limit freezes the score, but doesn't stop the game.

I'm not a cognitive scientist, but I suspect the pattern matching and fast addition are great exercise for the brain.

A little bit of room for polish: there could be a slicker way to try again. Resetting the cart works, but it feels a little clunky. Also, keeping track of the high score would be nice.

I'd give it a 10/11, on a scale that normally goes up to 10. Excellent, but there is a little room to make it even better.