Is it trying to be cute through subversion? Like that one puzzle in Braid that nobody could figure out. If not, then it's just bad design; press "Start" is as old as game themselves, no design pattern more deeply ingrained in players minds.

Aaah, I was ready to just close it and murmur that they didn't even test if the thing can be started on Ubuntu. That "start" totally looks like a button. And after reading your comment I tried WASD first, which doesn't work.

I made the same mistake.. Its perfect user feedback ;)