https://statsim.shinyapps.io/gamm/ We are currently on a free tier. The app can be offline if there's no hours left.

R -e "shiny::runGitHub('gamm', 'statsim')" (needs R and shiny installed)

If everything is ok, you'll see something like this:

Downloading https://github.com/statsim/gamm/archive/master.tar.gz
Loading required package: shiny
Loading required package: nlme
This is mgcv 1.8-28. For overview type 'help("mgcv-package")'.

Listening on https://127.0.0.1:5352

Then just open the link in the browser

R -e "shiny::runApp('./gamm')"