Halo: Combat Evolved Anniversary

The developer behind the original Halo’s makeover, 343 Industries, has released a video showing off the game’s ability to switch between decade old graphics and the shiny new visuals with the push of a button.

As explained in the demo, the hot-swapping is possible because two game codes are running simultaneously, the new stuff and the old stuff. The developer wanted this HD remake of the game to remind players of what it was like to play Halo for the first time, so the enemy AI is unchanged and the game controls exactly the same.