How can I turn a level into night mode?

I know that each theme has a corresponding night mode, that changes some properties, such as lower gravity. However, I can't figure out how to actually switch a theme over to night mode.

How can I switch a level over to it's night mode variant?

So after some additional messing around I managed to figure this out accidentally.

The Angry Sun has an alternate form: The Moon. The moon will fly at Mario like the sun does, but when colliding with Mario it'll actually destroy all enemies on screen (including the moon itself).

If you place the Angry Sun in your level, and then switch it over it's alternate Moon form, then the level will change to night. You can delete the moon after you've placed it, and the level will remain in the night theme. Switching the moon back to the sun will change the map back to the regular theme.

Additionally, after the first time you've switched a theme over to the night alternate, you can now toggle between the day and night themes via the theme switching menu.

It also appears that the Night Theme isn't available in the Super Mario 3D World game style, as the sun enemy isn't available.

The effects of the Night Theme seem to vary based on the theme. I'll attempt to document the changes here as I find them

• Ground: Night in the default theme just seems to be an aesthetic difference. If further experimentation reveals anything I'll update.
• Sky: Night theme has lower gravity, making mario jump slower and fall very slowly.
• Underground: Gravity is reversed (Aka mario walks upside down).
• Forest: Water becomes poison, and will kill the player upon impact.
• Underwater + Ghost House: Level becomes dark, with only a small area around you being visible. It appears other objects create light around them as well, but I'm not going to list them all here.
• Desert: Creates a wind affect, which activates periodically throughout the level. When active it'll push mario back, which essentially slows him down and makes his jumps shorter.
• Airship: Currently not sure if this does anything, but again, I'll update if I discover anything.
• Castle: Becomes an underwater castle theme.
• Snow: Snow and ice themed platforms (such as the default ground) becomes very, very slippery.