This mod will allow you to begin in the Lambda Complex portal and work your way backwards to the start of the game. Some areas require a bit of out-of-the-box thinking in order to precede without using cheats.
Play Half-Life in reverse, stating with the Lambda Complex teleporter all the way back. First fully playable version. * Added Hazard Course, because why not?
Finally Gordon goes to really fix everything :D
Really this the perfect version for this game