Speaking from someone that played the series in reverse, it's astounding how well it holds up. While I prefer the sequel, said sequel wouldn't have existed if this clever little title randomly popped into existence.

The only truly critical thing I think bogs it down is that it feels a lot like a Source Engine mod with the reused assets and sounds, but even that critique is meaningless when you remember that some of the best titles Valve ever produced were just mods given some love and production value.