I love how many retro games actually cared to try interesting little things to keep gameplay fresh, even if the base game was basically the same as many of its predecessors. While Satan’s Hollow (as evil-sounding is that is and possibly scary to many) borrows heavily from earlier fixed vertical shooters such as Galaga, Phoenix, and others, it manages to add its own little touches to make the game stand on its own.
While you’re just a ship trying to shoot down demons and other nasties of one type or the other, there’s also a bridge-building mechanic that gives you a bridge piece each time you kill an enemy and there’s not already a bridge piece out. You can take this piece and drag it over to the lava-covered right side of the screen (which becomes larger as stages progress, giving you less room — neat) and build a bridge over the lava to a stage to the right of the main screen that allows you to battle Satan himself (see, guys, you’re fighting Satan! It’s okay!). You also have a recharging shield that you can use for a bit to avoid taking damage from enemies and even kill enemies it touches, all the while keeping the enemies from stealing bridge pieces and even your extra lives (!).
It’s a pretty enjoyable game with nice mechanics, and yet probably not very well known. Go play.