Half-Life was released for the PC on November 20, 1998. The game was developed by Valve Software and was published by Sierra Entertainment (the deal with Sierra is now expired). Numerous expansion packs and mods followed in Half-Life's footsteps, such as Counter-Strike and Half-Life: Opposing Force. Half-Life: Blue Shift, a Half-Life expansion pack released on June 12, 2001, added the High Definition Pack, which included new models, weapons, and items. Due to Half-Life's huge success on the PC, it was then ported to the PlayStation 2 on October 29, 2001 by Gearbox Software. When Half-Life 2 was released on November 16, 2004, a Source version of Half-Life was also included. Half-Life: Source included the Havok physics system, dynamic lighting, new shaders, and improved A.I.
Many of the weapons were redesigned in the High Definition Pack. For example, in Half-Life, the machine gun in the game is an MP5. However, in the High Definition Pack, the machine gun is an M4 Carbine. Notice the brand new model below:
The High Definition Pack also included redesigned character models for almost every enemy and character in the game. Take a look at the original Half-Life zombie and the High Definition Pack one to the right.
Other than the redesigned models, the High Definition Pack did not change the gameplay in any way. Besides the original, the High Definition Pack can also be used with the expansion packs Blue Shift and Opposing Force.
The PlayStation 2 version also featured the High Definition Pack. However, the game ran at a very low resolution, so many areas looked unpolished and choppy. It also suffered from several framerate problems during intense battles.
The most memorable part of the PlayStation 2 version was the included co-op play (called Decay). It featured nine exclusive missions which are not available to the PC version of Half-Life. Both players assume the roles of scientists with completely different storylines. The PS2 version also gave the ability to play as a Vortigaunt (accessed by a cheat code). The single player campaign also has several level re-designs (which will be covered in the guide).
The PC version is still the winner in graphics, as it can support higher resolutions and can also come with the High Definition Pack.
Half-Life: Source featured full physics, Source shaders, dynamic lighting, and improved A.I. Although Half-Life: Source does not have the graphics of Half-Life 2, it still has several improvements. The water and lighting used in Half-Life 2 is now present in Half-Life: Source. Cubemaps are also used in Half-Life: Source. The A.I. for many enemies now follows Half-Life 2's A.I. system.
The Source engine also supports higher resolutions and features such as anti-aliasing and anisotropic filtering, which smooth jagged edges and improve texture quality, respectively. Half-Life: Source still uses the old models and textures from the original Half-Life, with some improvements.
The crossbow in Half-Life: Source now has the ability to impale enemies to the wall. All of the enemies in Half-Life: Source follow Half-Life 2's A.I. patterns (for example, the grunts in HL now use the Combine soldier A.I.). The crowbar swing speed and player movement speed are also much faster. Half-Life: Source also has the autosave feature disabled, so you can only save in the menu or quicksave.
When compared to the original, Half-Life: Source offers much better graphics with higher resolution support, shaders, AA and AF, and dynamic lighting. Below is a screenshot of Half-Life: Source's water:
The High Definition Pack is not available to Half-Life: Source however. Several of the exterior levels in Half-Life: Source also have 3D skyboxes, which means that there are 3D objects visible in the background instead of Half-Life's 2D backgrounds.
Half-Life: Source also features Half-Life 2's blood instead of the original's low detailed blood. However, several of the blood pools near corpses still use the original's blood, but any enemy, scientist, or guard, will use Half-Life 2's blood when hit.
The Source version also has brand new menu designs and a 3D background for the main menu, which is very similar to Half-Life 2's.