Intense cinematic action
The action in Ep1, like the other Half life games, consists mainly of intense shootouts with soldiers, battles with hordes of zombies and alien creatures with a puzzle solving element. The great thing about the game is that many of the combat sequences will be a puzzle in themselves, such as using a rollermine to distract a sniper's attention whilst you run from cover to cover.
A lot of emphasis in Ep1 is put on working cooperatively with Alyx, a bright, savvy girl with a knack for opening doors and shooting zombies in the head. There is a convention that female video cameras must have enormous breasts and not a great deal of personality, but Half life 2 completely shattered this with Alyx, who is uncannily human. Alyx is a big focus for the game. She is with you for almost the entire game, and often speaks her mind about the situation and gives helpful advice, even joking with the player. So what USEFUL things does she do? She will help you out a great deal in combat; she uses a fast firing glock pistol that is pretty effective at taking down mosnters and soldiers alike. She uses other weapons over the course of the game too, but I will leave this for you to find out.
The combat is as intense as ever; each type of enemy needs to be fought in a different way, and you will soon learn that you need to be careful to prioritise threats before they blow up in your face (literally in the case of the new enemy). One small problem is due to the very linear level design, the Combine Soldier AI is a little stifled; they are given little opportunity to flank or take cover and it often seems that their only option is to simply run towards the player.
The graphics are better than ever. The boys at Valve have added in some new graphical jubblies including specular lighting, higher resolution textures and HDR lighting. HDR lighting is a great new addition to the source engine; HDR stands for High Dynamic Range. This means bright lights can be really bright, wheras dark places can be really dark, but detail can be seen in both by way of automatic exposure control. This isn't just a fancy gimmick, it really makes an impact on the visual quality of the game. It especially improves the quality of reflections on water and other objects.
The reason why Alyx's speech and acting in the game is very important is because episode 1 isn't just a game really. It's more like a playable film. The downside of this is that it will play out in pretty much the same way each time you play it. The upside is that it is an absolutely staggering experience; everything about the game feels so real and detailed. I honestly don't think that any half life game or indeed any game has been so successful in immersing the player into the game world.
The game is six hours long, but the six hours are probably going to be some of the most explosive, detailed and fun six hours of gaming you've ever had.