Loop Mod is an addition to Black Mesa's On a Rail chapter, adding a couple areas to the very first map of the chapter. The mod reinstates the looped gameplay that was present in the original Half Life but was left out of Black Mesa, in part because the original design was deemed confusing. This issue has (hopefully) been done away with in the mod. It also reinstates three iconic areas from the original as well. The mod also fixes some design errors that were present in the original map. Comes with On a Rail Uncut compatibility.
Screenshots of the mod that compare their build to that of the original Half-Life.