Thank you for giving it a try, and I'm glad you liked the music and atmosphere! 😄
The issue was most likely caused by running both players on the same PC. The main gameplay is controlled by the host (Player 1), and when the host window loses focus, the game effectively pauses — enemies stop spawning and time stops progressing.
After the jam, I plan to add a bot companion mode for the main map and future maps, so the game can be enjoyed even when a second player isn't available. I also like your idea about a gameplay video, so I may add one in a future update!