You can lead aliens to enemy soldiers,or you can take down the soldiers with a rocket launcher. In Half-Life,you play Gordan Freeman,a recent recruit for the Black Messa researh facility. Your job mainly consists of risking your life to test dangerous materials. After one of the expirements goes wrong,you're left alone in an underground lab with aliens crawling everywhere and enemy soldiers waiting around every corner. At no time are you completely safe from some unseen danger.
Aliens leap out of vents,they hide under desks,they duck behind corners.
They figure out how to kill you and you have to counter their move. The soldiers are even tougher to beat. They work in teams,hide behind pillars,throw grenades,radio for help,sneak up behind you,shoot from above,set tripwires,and those are just the regular soldiers. There are also assasins who can run so fast that all you see is a black streak. As you can see,Half-Life is no walk in the park.