Maybe supertuxkart isn't in your path. Try to find where the executable is.
apt should be able to show you where it installed the filed.
Try something like
- {l Code}: {l Select All Code}
apt show supertuxkart
and see if it tells you where it installed it.
You can try searching the usual locations, e.g. /usr/local/bin or /usr/sbin/ etc.
Or you can do
- {l Code}: {l Select All Code}
ls -R -l / | grep supertuxkart
and see if it shows something like
/usr/local/sbin/supertuxkart
Then that full path is the command that will run the game.
Or you can install synaptic which is a gui for apt and search for it there.
Good luck!