Half-Life 2 Sandbox

Play Half-Life 2’s original campaign inside Garry’s Mod, starting on the opening train. Press Q to spawn props, NPCs and weapons. Build with the Physics Gun and Tool Gun, undo experiments, duplicate contraptions and use GMod’s normal saves while the original story and level transitions continue.

Solo. Requires installed Steam copies of Garry’s Mod and Half-Life 2. Melty installs and launches the mashup; the original maps, voices, music and scenes are read directly from your own Half-Life 2 installation. No game content is included in the download.

Campaign controls are under Q → Utilities → User → Half-Life 2 Campaign. You can restart the current level or start a new campaign. Sandbox experiments can interrupt story scenes; undo or a level restart lets you try again.

Tested: two five-minute Melty installation/gameplay runs, including the opening, native map transition, Q, prop spawning, physics, welding and undo. Additional checks passed in Water Hazard, Black Mesa East, Ravenholm, Highway 17, Nova Prospekt, the Citadel and the finale, including airboat/jeep seats and restoring stripped tools. These are chapter spot checks, not an exhaustive continuous campaign playthrough. The automated runs temporarily exclude unrelated add-ons; normal launches retain them.

Credits: Half-Life 2 by Valve; Garry’s Mod and Sandbox by Facepunch Studios. Original integration built for the creator with OpenAI Codex. Players supply the required games; their content remains with its owners.