Trying to open the playground link shows an error on the console =>
Error loading: https://unpkg.com/mithril@main

Click here to open the sample on flems.io =>

https://flems.io/#0=N4IgZglgNgpgziAXAbVAOwIYFsZJAOgAsAXLKEAGhAGMB7NYmBvEAXwvW10QICsEqdBk2J4s+LLQCuDABQATWtSk4G+AEa15ATwoACYAB00e03oBuEGAHdEesDOrEI9WQEoDxs970AnGMRSviZYsgDkhACMYfphACq+2no4etLEYW5eZqzGrG6UIHAwsE4uaAg8ACyIAExsHCCYOHj41HACNPSMzDxsALpUUBBoANYVqI1cYhDEhL7QAAJYGMMFQeQ8JMQADnCIAPT7MtsjAOattFj7WDNzi8urVMTa29yF1PPboqx9rEA