Terribly easy

Do you know what the worst enemy in the game is?

Stairs! or anything you need to jump on or over.
I bought one weapon and just kept upgrading it luckily I didnt buy any other weapons so the auto weapon swap was minimized.
I beat half the game just running and shooting with minimal aim then I switched the controls to button instead of joystick. That was helpful with the jumps but now you cant jump forwards and shoot but thats not a big problem because you can just keep running and shooting and eventually health and more ammo will drop. So I beat the rest of the game pretty quickly on my first try.

Free game so not a bad waste of 10 minutes or so.

ledmage about Desert Slug, v1.5