Full compatibility with the original Half-Life entity set
Support for forming complex hierarchies of entities (Parent System)
Mirrors that can skip reflection of any specified object or, conversely, show ordinarily invisible objects
Surveillance monitors (colour and monochrome)
Portals that can take you from one point to another (as in Portal, but more basic)
Weather effects (rain and snow)
A powerful particle system with a standalone visual editor
A system of prefixes for making complex scripted scenes
An extended decal projection system that works on both level geometry and characters (players and NPCs)
Realistic lasers that can be reflected off mirror surfaces (used in gameplay)
A large set of logical entities for implementing any conditions in scripted scenes or complex arrangements
A camera with flexible settings for cutscenes, letting you switch to any character's point of view (including inanimate ones)
Configuration options for setting the attitude of any NPC towards others and towards the player
Dynamic coloured lighting that can project and play an animated texture as a light source
Playback of AVI files on level polygons and brush objects
A 3D skybox for simulating expansive areas
Bloom effects
Supports for HD textures (up to 4096×4096)
Background maps in the game menu (as in Source)
Support for large game levels (32768x32768x32768 units)
Shadow maps for dynamic shadows
More believable lighting
Realistic rigid body physics powered by a third-party engine (
PhysX)
Realistic water
Dynamic day and night cycles