Walkthrough

Basics

The screen layout shows your score and lives in the top left hand corner; your remaining energy and your immediate enemy's remaining energy in the top right hand corner and in the middle any firearm you are holding, plus it's remaining ammo, or if you have the super strength or super run power-up then that will be there instead with a countdown of how many more seconds it will last for. Otherwise without one of those power-ups the middle area will be blank.

As you defeat enemies along the way some release power-ups. These are as follows:

LIFE	This replenishes your energy
1UP	Extra life
G	Gun - has 30 shots
R	Rifle - has 10 shots
SS	Super stength - makes you stronger and faster (maybe not as good as having a firearm so avoid if you do have one). This lasts for 40 seconds.
SR	Super run - use this to run through the level really quickly as you turn invincible but it only lasts for 5 seconds

Once all your lives are lost you can continue from the beginning of the level you died in (if you press to continue within the designated 10 seconds). There are three continues.