Delta Particles

Delta Particles is a single-player, story-driven, total conversion modification for Half-Life 1. Features include a new single-player campaign consisting of 4 chapters, total conversion, a lot of new content, the atmosphere of the new scientific complex "Delta Base", new weapons, a new Dark Ambient soundtrack and a BlueShift-style XEN level.

The plot takes place at the universe of HL. You take the role of Nick Farrell, a technical engineer in Delta Base - the complex that competes with Black Mesa in various research fields including exploration of the borderworld Xen and weapon development. Due to accidental entanglement of two different experiments conducted at the same time the infamous resonance cascade affects the Delta Base as well, bringing the hostile alien lifeforms which infest the facility very soon.