The main mechanic of the game is that you are constantly moving in one direction, and shooting allows you to switch directions.
The music is awesome, and combined with the explosive feel of the game it made me feel like a boss.
I hardly ever felt like I was fighting the game's flow. There were times where I felt like I had to wrestle with the game, but for the most part I was able to just "go with the flow" of the game.
There are coins that can sometimes be picked up from killed enemies, but there is no store. Instead, all they do is add 5 points to your score.
There is no options menu. It doesn't matter much to me, but I imagine not even being given the option to change the volume of the music and sound effects or to lower or raise the quality of graphical effects might annoy some people.