system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: That euphoric half-asleep feeling where you're still semi-present but your mind is also solving tangential abstract problems that you can never remember upon fully waking.
gpt
One definition of a brain is that it is a "meaning making machine", it takes stimuli from your sensory organs (eyes, ears etc) and constructs a mental picture of the world.

We still have a fairly rudimentary understanding of how brains achieve this, and whilst we know that sleep is essential for survival, we don't have a solid answer on exactly what's going on, but we do know that a huge amount of (seemingly random) brain activity occurs during REM sleep.

I think the experience you describe is the product of your brain trying to make sense of the scrambled messages as bits of it wake up and other bits are still asleep.