The part I enjoyed the least in the experience was the interminable tutorial, which plays every time you start a game. I needed the information within it, but I wasn't willing to bear with the sequence of text bubbles. I would strongly recommend tutorialising things in game directly when it's necessary to use a certain function. You could have also placed the A and D keys visually directly on the player's cursor, tinted them the colours you did and the tint true and false the same colour. Done. No need for tutorial at all.
The graphics are simple, abstract and coherent. It's all very teal, but that's a matter of taste. In contrast, I think the colours you picked for the bullets are too unsubtle. #FF0000 and #00FF00 are not exactly a match for your art style, and they are a nightmare for people with colour blindness.
I'm not a fan of uncontrolled randomness in skill based games such as your own. The ??? tiles affect my playing experience negatively. I know you wanted to stick to the theme at least to some extent, but I don't think it justifies damaging your design. With that said, I do think the game benefits from having a wildcard. But you should brainstorm to find a way to make it somewhat predictable.
Audio was solid. I really liked the SFX for moving left and right, but it did mislead me to think that it would be a rhythm game. Not sure this information is that useful, but there... :)
Decent entry.