It's like Alice in Wonderland, constant juxtaposition of the very large and the very small, an extermination machine that doubles as a wildlife reserve, the underground & overground (but also the innerground and outerground). Tiny cramped hallways that open into gigantic vistas.
Halo always reminds you it's fake, and makes jokes of its undisguised simulation like a dream. A tiny island conceals a bottomless chamber. A spectacular light show frames a genocide button. Levels are loops inside mirrors. You return to T&R upside down, then go down, then go up.