Source: callout-paper-fold.css

To override the values defining the folding angle, use the snippet:

/* Define the starting folding */
.callout[data-callout="paper-fold"] {
    --corner-diag: 100px;
    --corner-angle: 30deg;
}

/* Define the final folding on hover */
.callout[data-callout="paper-fold"]:hover {
    --corner-diag: 10px;
    --corner-angle: 60deg;
}

CSS Variables

Variable	Description	Default value
--paper-fold-corner-diag	Length of the diagonal of the folding part	100px (25px on mobile)
--paper-fold-corner-diag-hover	Length of the diagonal of the folding part on hover	10px
--paper-fold-corner-angle	Angle of the folding part	30deg (70deg on mobile)
--paper-fold-corner-angle-hover	Angle of the folding part on hover	60deg
--paper-fold-color	Color of the paper fold	255, 247, 64 in light mode, 255, 255, 153 in dark mode