You need the chrome browser for it to work, but this is wonderfully addicting. If you rather use your browser rather than phone, you can click the 'No smartphone? Play with PC only.' link at the bottom.
It's literally probably the most interesting thing I've seen in a really long time. I have a bit of a hard time controlling it with my phone, but I think that's more just because I seem to grossly overdo all my tilts. Still crazy addicting.