If you ever played Naughty Dog's superb - and for me still best game - Uncharted 2, you'll remember the train level.
Chapter 13 - Locomotion sees Uncharted's wise-cracking star Nathan Drake move up through a speeding train, fighting off scores of enemy mercenaries and even a missile-firing helicopter.
The level was eye-catching for a number of reasons, chief among them the feeling of realism the train journey provided. It felt like the train, with you on it, was moving through an actual environment, through a jungle, tunnels, out onto cliffs and ever onwards - in a relatively straight line - to its and the level's final destination.
How did Naughty dog do it? A new video from YouTuber Freako, who works on the Boundary Break video series, reveals the secrets of Uncharted 2's train level.
It turns out the train level is built around a couple of big loops. Freako uses the game's debug menu to mess with Uncharted 2 in ways never intended by the developers. He can move the camera about to reveal areas outside of the player's normal vision. Doing this, we can see the huge loop the train travels on, creating the illusion of forward progress. We can also see just how long the train actually is, and the huge size of the environments.
Naughty Dog also uses clever tricks to load in new areas without the player noticing, such as putting up high train car sides you can't see over, or triggering cutscenes in order to mask area transitions.
You best illusions are those you don't realise are illusions, and that's what Uncharted 2's train level feels like to play. It's an action movie rollercoaster ride in video game form that moves so fast you can't see the tricks that fuel it.