Cannot read properties of undefined (reading 'end')

[JeroenReumkens]

I just got the error below when running this repository and inspecting the H2 "Can you make the font bigger?". I'm not sure what's causing this, but I thought it would make sense to report this.

Perhaps it's related to the classnames you try to show, which in this case include a backslash.

[TimChinye]

The reason why this happens is that the tool doesn't accept a "normal" timeline range; instead, a <timeline-range-name> (e.g., cover, contain, etc.) must be specified.

A temporary solution that OP could implement would be to change animation-range: 0% 60%; to animation-range: cover 0% cover 60%;.

If you have any 0% (only on -range-start) or 100% (only on -range-end), you can replace that with normal if you wish.