Some of the sprites don't work. The sounds are too loud and harsh, which is scary. I think the idea itself fits the theme well.
Please, if you can play the Gd Games version. The html version has some graphical problems (I don’t know exactly why, I guess is a GDevelop 5 bug): https://gd.games/kolde/the-cosmic-postman-and-the-sec
The sounds… I hadn’t time to implement a volume option. In my PC and mobile are balanced, but in others can be differences. Try to low the volume to 50%
Anyway, thanks for the feedback! I appreciate a lot (things to fix in other jams hehe).