The mushrooms are using standard shader material with some emission.
Combine that with some bloom and you achive this effect. In order for this to work correctly you also need to change color space from gamma to linear. You can do so in Project Settings > Player > Other Settings. I always use bloom along side Color Grading with Mode set to ACES and Post-exposure set to about 1 so it's not so dark.
I always use bloom along side Color Grading with Mode set to ACES and Post-exposure set to about 1 so it's not so dark.
Make sure you also have HDR enabled in Project Settings > Graphics. It should be enabled by default.
I'm gonna expand this game. If you are interested in it then follow me on itch.io page. Thanks for playing!