Anyone who has played a lot of vertical shooters will know it's necessary to have an 'enemy battle-fleet watery-bit' stage. Here's Gun Frontiers complete with little landing craft dropping of tiny geezers (in green on the left) and a sub..

Actually the sub mini-boss turns out to be a major pain as it fires volleys of missiles at your plane which can only be avoided if you are quick-witted enough. Lucky for me it's gonna dive off in a mo..

Until you finally get the better of it.. Yeah.. right back at you matey!! Safe at last!!

..OH S*$%t!!.. Here's what stands between you and the end of level three.. a MASSIVE fortress guarding an enormous dam.. I've stuck a load of screens together to give you some idea of the scale of the thing against your ship (bottom right).. You'll need to take out each seperate gun turret (plus the huge main gun) to defeat it..