From StrategyWiki, the video game walkthrough and strategy guide wiki
Expect this game to be hard the first time you play. There are certainly a number of things you need to do to get through the single player campaign. There are also obstacles you need to overcome if you want to slow the flow of enemies.
- Enemies will keep respawning until you destroy their source. Once you find a source like the conduit, you can take it down with a grenade and a lot of ammo to stop the flow of enemies so that your gun won't run on empty and slow your progress down.
- Your ASE will alert you to many secrets. You need use it a lot if you want to unlock sections, change weapons, find secrets and most importantly take down invisible bombs.
- With minibosses, you need to lock on so you know how far you have come to taking them down, which could take a lot of hits. Once the green bar goes empty, the enemy has died.
- You'll encounter TVs and radios, which give further background info about the conspiracy around the alien invasion. You can stop and rest up until you are ready to continue on the mission to find the source of the aliens.