Hey, I've had this experience almost perfectly. It's brutal, it's called burnout, and it takes a while to recover from. Loosely, it's depression, but specifically within the context of your personal connection with work. I burnt out for the second time in March 2022, and it took about a year to start having the desire to code again, and another 3/4 of a year to find another job. When I get into this state, I almost always get terminated, so you might have that to look forward to, but it's a learning experience.

Step 1) Search "guide to burnout hacker news" and just read the recent or not-so-recent threads.

Step 2) Probably lower your expectations of yourself on a day-to-day basis. Do the absolute bare minimum to stay employed.

Step 3) If you can, see a therapist

Step 4) Forget about the game for now and don't guilt yourself about it. Realistically it probably wasn't going to get off the ground anyway, and consider it a learning experience. If you give it some time and want to come back to it, you'll probably have a renewed enthusiasm, but not if you just look at the source code folder and guilt yourself about it. Detach yourself from this idea—especially for those of us with ADHD—that you'll stay interested in the same things over time, or that you should. Let it happen naturally, explore some other ideas, technical or otherwise, see what does it for you if anything.

Step 5) Take a leave of a month if you can financially (but regardless of if your employer wants you too), and see if that changes things.

Step 6) Spend that month closer to nature

I was just about on the verge of burnout recently, but I just literally got on a plane and left. I risked my job to do that, team didn't like it, but I was risking my career yet again if I didn't do it.