I'm playing the original Raiden game, which is breaking my balls btw, but after 3 continues I can't go any further because it wants more coins, alas I haven't gone further than stage 2.
Is there a way to insert extra coins?

Anyway I'm getting the impression this game was designed for two players and it would have been nice to have coupled the single player controls on both ships.

I can only speak for Raiden Fighters 2 and Raiden Fighters Jet (Since I haven't tried the others yet...)

The default key for Start/Coins is [Enter]

You can reconfigure the keys in the in-game options menu including the coin key.

Hope that helps. ^_^

It's my impression that the game has a fixed amount of credits and lives. When you run out , its indeed game over. I tried the advice of mapping the controls and it only leads to that particular issue of running out of credits.

Talk about an all skill game, this is one of those games where you know you get your moneys worth and be greatful you are not in the arcades spending quarters after quarters.

Although it is frustrating when you can't get past certain enemies. Thankfully there is Youtube, and Game FAQS to guide you in mastering these game.s