Ambient 64 is a hack made by MilkWine for the Dream Themed Level Competition, in which it placed 38th. This was the creator's first hack, and they used the competition as a chance to learn more about working with decomp.
There is one level in this hack, which is registered as a hub world. It is an island in the sky covered with grass paths outlined by brick steps; there are invisible barriers preventing Mario from jumping off the edge. One path leads to the top of a waterfallpouring down from the island- jumping into it will apparently kill Mario and send the camera back to the Starting position, without respawning Mario or granting a Game Over.
A short ambient experience. No Stars, no game, just sounds and a tiny dreamlike space to run around in. First romhack. Spent most of the time learning the decomp workflow. Thanks a ton to the SimpleFlips discord for all of the resources, and thanks to cozies and kurethedead from the Fast64 discord for help understanding SM64 rigging limitations.
And of course thanks to SimpleFlips for exposing me to the world of SM64 romhacking. I watched all of the competition videos, and then proceeded to do none of it. Still fun though.