Makers! What was your first MVP?

Recently I had a few ideas in mind and hence started looking for the best ways to understand if the market needs it. I knew about MVP since long, but now wanted to identify the most innovative ways to make validation quick and apt. For the same, I explored over the Internet and Twitter and ended up writing a few points I found useful @ https://pranavv.substack.com/p/v... Though, I feel there's still more validation/MVP ideas out there which I haven't came across, and hence decided to start a discussion. My question to makers is: What was your very first MVP? If possible mention the assumption you solved. Hope you love answering this! Thanks :)