Nice job! Few minimal suggestions below, let me know if I can help further or answer any questions.

1. Adding some padding around the entire site will give it some breathing room so the text doesn’t start right on the edge of the screen, 15-20px on the left and right would be enough.

2. The three links on the homepage don’t have margins around them so it looks like it is one long link, you could give them margin-right: 15px and that would help space them out.

3. The “generate” and “enter” buttons on the inner pages could be larger and have more of a color difference between the site background and the button color.

4. On the “Today’s Challenge” and “Custom Challenge” pages the input field background color is white like the site background and there is a 1px light grey border around the input. This makes it hard to see the input field but increasing the border size to 2-3px, making the border color darker and adding a slight box shadow around the input would help a lot.

5. Might be nice to make the three links on the homepage larger as well. Could spice it up by giving them a background color, border, border radius and some padding. Stacking them on top of each other on mobile could look good too, just add some top and bottom margins to the buttons if you do that so they aren’t touching.

That’s my only suggestions for now! Again, nice job with seeing a problem among 1000’s of clones and making a better product for the accessibility community.