Some Black Mesa: Source gameplay has been leaked. Black Mesa: Source is an ongoing fan project which aims to re-create the original Half-Life using HD visuals. The footage below is from the "On a Rail" chapter, where Freeman must navigate through an electrified rail yard teeming in guards in order to launch a rocket. While the voice-acting may need a bit of work, everything else from the guns to the music seems top notch.
Source: ValveTime
