This is my entry for the 20th Ludum Dare. I did not finish what I set out to do: Six hours before the submission deadline I noticed there weren't any levels or stuff and programming the level editor took way more time than estimated. I will continue to work on this when the time comes.
Controls:
Arrow keys to move, Tab to select a gun from the weapon stack, Space to shoot the equipped gun (autoselecting the gun was one feature that would have been implemented after the level was finished

I also made a timelapse video of almost the whole thing: