ChoRenSha 68K is an awesome shoot-em-up game with an old-school feel to it. There is never a dull moment, as even one hit from an enemy ship will kill you (unless you're using a shield).
The graphics are average. The background repeats itself, but it really doesn't matter because you'll be focused on all the action on top of it. The music has a nostalgic feel to it, and it makes me feel like I'm playing a game from the early 90's.
As for the controls, they are very simple--use Z to shoot using your normal weapon (and to start the game), and X to shoot the 'Bombs'. I also found that Q pauses the game. And if you die after getting far into the game, don't worry--a 'Continue' feature is included in the game, and comes in very handy in these types of situations!
The fast-paced action will keep you hooked for hours. 68K is definitely going to be one of the best games you'll ever play, especially if you're into old-style shooters. Try it out, you won't be disappointed!