Perhaps you can draw some inspiration from how Keen (1, 2, 3, 4, 5, 6) and Vinyl: Goddess from Mars did it?

Watch a video and read the full post including example code: http://www.zirthian.qubiqinteractive.ca/spaceship-control-and-physics.php

In this post I am going to talk abut two important things my arcade-style side-scroller shoot-'em up game: spaceship control and physics.

The game makes full use of …