The Ultimate Orange Box

The Ultimate Orange Box was released by Valve in conjunction with 984 Studios, in an attempt to give fans of Half-Life the games they deserve without Steam membership being required (though you can connect to Steam and use it at any time). It also utilizes a new engine called Source+, developed by 984 Studios, which allows for more detail and is compatible with any mod running on regular Source.

The Games
Several games were included and remastered for The Ultimate Orange Box. What follows is a list of games followed by their fixes.

Half-Life/Blue Shift/Opposing Force/Decay
 * Game upgraded in the Source+ engine
 * Bot multiplayer which adapts to your playing style
 * Game can be switched from Source+ to GoldSrc at any time

Half-Life 2/Episode One/Episode Two/Deathmatch
 * Game upgraded in the Source+ engine
 * Bot multiplayer which adapts to your playing style
 * Online co-op allows you to play as Adrian Shepard, the US Marine from Opposing Force

Portal
 * Game upgraded in the Source+ engine
 * All DLC rooms included
 * Video walkthroughs for each level if you get stuck

Counter-Strike
 * Game upgraded in the Source+ engine
 * Weapons from CSO, Operation Stopping Power, and the map as_oilrig are available
 * Bot multiplayer which adapts to your playing style
 * Can be switched between Source+ and GoldSrc at any time
 * Fully fledged single-player campaign has you playing as either a counter-terrorist officer or a well-respected terrorist: up to four-player multiplayer co-op and squad tactics for single player bots
 * Includes Condition Zero campaign as an arcade mode, complete with challenges for each level
 * Permanent and temporary attachment system includes underbarrel shotguns, extended magazines, and holographic sights

Day of Defeat
 * Game upgraded in the Source+ engine
 * Bot multiplayer which adapts to your playing style
 * More maps and weapons allow you to play as British, Russians, Japanese
 * Full single player campaign for each side
 * Can be switched between Source+ and GoldSrc at any time

Team Fortress Classic
 * Game upgraded in the Source+ engine
 * Bot multiplayer which adapts to your playing stye
 * Single-player campaign for red and blue teams
 * Can be switched between Source+ and GoldSrc at any time

Team Fortress 2
 * Game upgraded in the Source+ engine
 * Bot multiplayer which adapts to your playing style, and can use Scout/Spy bots
 * Fully-fledged single-player campaign takes place on the side of Green Reconstruction Negotiations (GRN), which defeats RED and BLU only for the Combine to attack early. GRN, RED, and BLU must push back the Combine for victory
 * Single-player allows for a full team of nine soldiers with three lives for each: when lives run out, the soldier does not come back
 * Hot-swapping allows for class switching on-the-fly on the battlefield: point and swap. Auto hot-swap when you die
 * Squad commands: anyone else on your team can be ordered to do basic commands or advanced commands specific to class
 * All hats, upgrade weapons, etc. included with the game (this includes promotional weaponry), but must be unlocked
 * Unused weapons with models unlockable

Left 4 Dead
 * Game upgraded in the Source+ engine
 * Bots adapt to your playing style in both single and multiplayer
 * Forwards compatibility: use Survivors and maps from Left 4 Dead 2
 * All current DLC included
 * Left 4 Speed unlockable as a bonus movie

Left 4 Dead 2
 * Game upgraded in the Source+ engine
 * Bots adapt to your playing style in both single and multiplayer
 * All international weapons included
 * All current DLC included
 * M60/Fallen Survivor/Golf Club placed into other campaigns
 * All Mutators available as challenge game modes
 * Backwards compatibility: use Survivors and maps from Left 4 Dead
 * Left 4 Speed 2 unlockable as a bonus movie

Garry's Mod
 * Game upgraded in the Source+ engine
 * SWEPS include weapons from every game, like TFC Minigun, Half-Life 1 shotgun, Portal gun, Left 4 Dead 2 Magnum, etc.
 * Attachment set from Pimp My Gun included with 3D weapon editor, allowing you to belt attachments onto your favorite guns and save them as your own SWEPs
 * All character models from games in this package are included