River Raid is one of those games that simply just gets better over time. Don't let the simple graphics mistaken you for how good this game is.
River raid is a top view plane shooting game that your goal is to shoot out ships and aircraft that comes your way. using the trigger button to fire you use your infinite ammo to blast your enemies away. The controls are quite simple up is to go forward (this also burns your fuel faster), back to slow down and come to a stop, and then your side controls to the right and left.
As mentioned you need to worry about your fuel load and along the way there are pink and white fuel markers. These are ships that will allow you to fuel up along the way. The longer you stay on one the more fuel you will take on till your full. Like in any fuel driven game, outside of shooting enemies you have to work on your fuel management. The higher the level the more challenging it is and less places there will be to fuel up.
Becareful that you do not shoot out your fuel ships cause if you do you will have to go on till you find the next one.