Thank you for the feedback. There is a peek of more content to indicate it is swipe-able to see more. Kind of like websites do with images, like Netflix for example.

Do you think if it was 100%, then people would still understand they could swipe?

Your site is simple to use. This is good. It also means that users won't need much help before they are proficient. But by reducing the screen width, you're punishing your users forever. You can solve this by teaching users about the interaction up front. Try placing some text somewhere on the screen that encourages users to swipe. You can hide it once they've done it once. Alternatively, shortly after page load you can animate the page to peek the next column of content. It will require a little playing around so that the instruction is clear but unobtrusive.

What phone are you using right now? That would be helpful for me to consider. I did increase the column width from 320 to 335 pixels based on your feedback. It does feel better. But if I make it too wide, then the content can get too big I feel.

I'll be thinking more about this feedback and will test some more. Thank you!

Just for an extra data point, I really like it the way it is. Seeing a peek of the next column to give an intuitive understanding that you can swipe for more is really neat (and I'm on an iPhone 8, so not a particularly large screen).

Thank you for that data! I was thinking about making it even wider, but that could hurt usability on smaller phones....

Ok I made it a bit wider, I hope it helps a bit. Will think about doing 100% on mobile...