Proto:Half-Life (PC)

The September 1997 prototype of Half-Life is from before the game was completely redesigned and rewritten. Many differences exist at this point, including the plot, locations, and general concept. Originally meant as a press demo, the game was leaked to Reddit in January 2013.

The physical disc sold on eBay for $709 US. Notably, the place of origin on the listing was "Bellevue, WA", indicating that the leak might have been internal.

Plot Differences
As the game received a full rewrite, the plot is very different from the final, including:
 * Instead of Black Mesa, the game took place in an abandoned missile silo only referred to as "The Silo".
 * Gordon was originally meant to be "a weapons research scientist who has never touched a weapon".
 * The Silo was meant to have already developed a Portal, however the Portal was completely contained.
 * Gordon's lab had nothing to do with the incursion. Instead, the Portal's power core goes critical, causing it to rend space-time and producing the same effect the resonance cascade does in the finished product.
 * The rest of the plot is essentially the same, with the inclusion of acquiring "a device which means the difference between victory and annihilation".

Video Overview
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The disc includes a series of demo videos recorded by a Valve employee (potentially Gabe Newell himself), and showcases each of the disc's levels. A video has been compiled of each of these demo files. This video shows multiple features that don't actually work in this build, including the Human Sergeant enemy.

(Please note that as of June 28, 2013 the video is bugged and may only play a minute of the content. Links are present to each section on the YouTube page.)

Early Quake Leftovers
Several raw uncompiled BMPs lie in the GFX folders that pertain to several graphics lumps used by Quake. Part of it are unused "dead" faces and variants on the quad damage face in which he licks around his mouth.

The palette was shifted and recalculated.