Xenion

Xenion is an ambitious scrolling arcade game in the vein of the arcade game Xevious although honestly I think this version is more complex. The basic premise is that you are attacking an evil alien race in their own solar system, flying between 4 planets (which you can see above in the 2nd intro screen). The game runs in a 4 color mode, but makes great use of it's color palette (black, blue, green and white), including widely varying terrain (out in space, over oceans, alien cities, cratered landscapes, etc.), plus 27 different types of aliens, a variety of ground based aliens and alien structures to shoot (tanks, force field generators, radar stations, etc.) There are also some pickups for the player - an "E" to charge up your shield energy, and something that looks like a key that gives you a smart bomb.

The game is operated by a single button joystick, with the SPACEBAR serving as your smart bomb button (which destroys most aliens on the screen - motherships and force fields excluded). You can also pause the game at any time, and each time you die or complete a solar system, the game will pause until you hit the joystick button to resume play. The game also features auto-fire on the joystick, so it's not technically a button masher. It does feature a fairly advance graphical layering system internally