Beat on normal. For the first few levels I did not know there was a button to lock your direction and thus found the game quite difficult. SMG was my go to weapon. In the subway level I got lost and checked a walkthrough; that is how I found out about the lock. That changes the game!

With direction lock my go to weapon was the pistol for its strafing and backpedaling. Most enemies were easy to defeat with a bit of footwork. I barely used the shotgun because it lacked the range of the pistol and put a delay on dodging. I mostly used it vs enemies hiding around corners and cover. The SMG was still the overall best weapon. At first I was annoyed that you cannot shoot and move at the same time but once I got used to the alternate aiming I found it excellent for hitting enemies that were slightly off center faster than repositioning. I found the red shirt enemies the most difficult because of their unpredictability and saved the flamethrower for them. Early on I used grenades to kill the assault rifle guys while later I saved them for enemies that were unreachable. Only used mines in the final boss fight; used flamethrower on the rocket guys and SMG for the boss. I liked luring enemies into friendly fire grenades and mines.

I did not really like the boss fights (including the ones that were lots of enemies) though I only had to endure deaths before I knew about lock. Died a couple times in the jet level because of its low hp and difficulty in avoiding shots; it did not play like a normal scrolling shoot em up. This is a great game that is almost up there with Doom and Goldeneye 64. Biggest flaw is lack of a map, which the game really does need.