The visuals (to me) are perfect for this type of game. Based upon the scroll at game beginning, it appears you made these! Outstanding!
As for the game itself, it plays a little fast for me but then the original River Raid was also too fast for me.
I have tried to follow code but it is well beyond me ( I am an ancient mainframe programmer), I am interested in breaking your code down to smaller chunks to execute to try and better understand. Is it possible to get access to your images?
If not then I will just enjoy playing your game.