You can't get anymore retro than this classic shoot-em-up game. It's a simple game with simple graphics, but it has one of the most vital assets for any computer game: gameplay. Modern games seem to forget this with their fancy "3D graphics" and "millions of dollars". All you need is a pointy green thing which shoots… (more) white stuff at a rampaging invasion of wobbling blobs. They don't make 'em like they used to. Featuring High Scores!

Press Space Bar to fire, move left and right using your arrow keys. P to pause, Q to quit.

Source: http://www.widgetbox.com/widget/space-invaders