Button is low contrast on bright button.

(https://rhys_vdw.itch.io/enter-the-chronosphere)

Leafo:
"The color of the button should be legible by comparing the brightness component of the button color but I guess the algorithm is off for this case."

From older issue: https://itch.io/t/257379/theme-button-text-color

The only options I can suggest is to either use a different button colour, or to request custom CSS from support for your project and change it yourself. Although I’m not certain if the colour of the button is allowed to be changed through custom CSS, it’s worth a try.