We are also playing a lot of different games with balls like basketball, volleyball, football tennis - a special game where a small ball is played over low net by legs/feet and head etc.
This game is immensely popular in CZ and Wikipedia even says that the first-ever match was played in 1922 in Prague. We call it "nohejbal"("noha" = "foot")
It's a lot of fun, but it is very rarely played by women. Thus, it's kind of interesting that Petra plays it. It must be much more difficult with a tennis ball!