[quote name='Cocojames333']How is this game? Extremely difficult?[/QUOTE]
Nah.. The hardest difficulty (nightmare, I think?) is not hard at all.
Either keep moving, or just take quick cover and shoot. Most of the monsters are slow anyway. The ones that shoots guns are somewhat dumb, and the ones that shoots projectiles, have slow traveling projectiles; so they're easy to avoid.
You'll pick up on the AI pattern quickly.