What operating system are you on?
What is the general configuration of your PC?
Thank you for getting back to me so quickly, and thank your developer friend, too!
I went through the tutorial again, and now I can create a new player and play the game.
However, I am afraid of losing my progress again. Can you suggest ways to prevent this problem again? Or do I have to manually back up my save file every time? And where are the relevant save files anyway?
The pleasure is mine!
I don't think you need to "fear" losing your save. In reality, I imagine your previous save must be somewhere in the system.
But anyway this is out of my control as it's a Windows10 update (I can't imagine any other reason for this problem, it's never happened before).
Next Jump was our first game (from 2017!) and has already received a free expansion (called Red Legionnaires).
We're about to release a "spiritual successor" of it, but for now only on Steam:
https://store.steampowered.com/app/1932210/Takara_Cards/
Thank you very much for playing our games! :)