The above site displays the following message instead of rendering WebGL:
Link Error: Internal error compiling shader with Metal backend.
Please submit this shader or website as a bug to https://bugs.webkit.org”
iOS 15.1 iPad Pro (11-inch) (2nd generation)
Thanks for the report.
You can most likely work around this by changing the function name "and" to something else, like "myand":
bool and(int x, int y)
return mod(float(x), exp2(float(y))) != 0.0;
The fix will be shipped in a future update.
*** This bug has been marked as a duplicate of bug 229378 ***