The key thing to getting far is to get plenty of options and power ups early on in stage 1, and try not to focus on everything on screen, as you will get distracted and easily snuffed out.
Word life.. and get the ripple laser. I noticed if you flip on the turbo and hold it down all the ripple shots from the options will slow the game down, giving
to a little extra time to see what's coming.
And Gunner, if you're still stuck on the brain try this:
1. Hang in the upper left corner.
2. Before the brain moves he'll extend his arms, wait for him to fully extend his arms toward you. Dodge any bullets.
3. As soon as he starts moving swoop under him to the lower right of the screen, make him follow you
back a bit so that there's good clearance in front of him.
4. Quickly move up and circle back around to the front of the brain. Watch the positioning of his hands while you do this.
If the hands won't let you move up then just pull back to the left and use the same technique in reverse.
5. Shoot him in the eye for a little bit. You win.
Be careful not to fire while you're performing steps 2-4.. that'll slow the game down and give the Brain
a step on you, it seems like he catches you quicker when the game slows down. So hold your fire and
circle around quick.