During game play, holding the top four buttons together will bring up a screen 
which allows you to adjust the resolution and move the screen around to your 
liking, in addition to several other features.

Watch for trees that are slightly off color, generally on the right side of the 
screen which stop your fire. Once found get close to them and unload into 
them until an explosion releases a flying pixie. Capture her immediately. Don't 
know what immediate benefit the pixie is, but when you die she will release 
power ups for you.

To have unlimmited continues go to the credits screen then press all four buttons 
triangle, circle, X, square. You will see a new option called freeplay. 
Now you have unlimited continues.

In the difficulty settings screen hold R1, R2, L2 and L1 together. While 
holding them down, press start. This will enable you to choose from 
missions 1, 2 or 3.