GunNail (1992)

Gunnail is a vertical space shoot'em up. It's a very standard shooter - very fast action, and many enemies to kill. Player controls a space ship, and flies straight forward. He must destroy enemies - the spacecraft has a gun that can be improved by power-ups and special weapons. Player can obtain helpers ("option" from Gradius). At the end of each level a boss awaits - every boss is heavily armed and difficult to destroy.