A buddy of mine picked this one up recently and was talking to me about it, asking some questions because he was having a tough time with it. Now I've had a copy for at least a decade and probably hadn't played it in about half that time, so I decided to fire it up for a refresher. Playing through the game took me a while, and a couple of tries, and when I finally made it to the boss in the Skynet level, I ended up burning through all of my continues and almost all of my lives before I finally beat the giant bouncing Terminator head (which kind of reminds me of Zombie Nation). Holy crap, does that thing take a ton of damage. That was about a 15-20 minute boss fight, no exaggeration. Sheesh! Fortunately, he drops weapons and power-ups throughout the fight, and because you rack up so many points blasting away at him and his minions, you'll occasionally earn a bonus life.
Throughout the first 9 levels, there are numerous health and one ups to be found throughout each maze-like stage, which makes the game manageable in spite of its difficulty. I mean, there is a steady barrage of bullets and projectiles coming your way throughout the game, so it is definitely tough. I learned that if I had a good weapon to swap it out when I was about to die so that I didn't lose it. You can carry two weapons at a time, and can swap between them with the A button, so it's recommended to switch to your less powerful one when your health is getting low. And whenever you respawn, you're invincible for several seconds, so that's a good time to just plow through a difficult spot in the level as quickly as possible, thereby skipping through enemies. And the boss fights all have set patterns which you can pick up on fairly easily with a little practice. After I mastered these techniques, the game was much easier to manage.