Focus your time on the browsers/platforms the majority of users are using rather building for the newest and letting the rest settle. IMO, however, building for the newest promotes innovation and encourage users to upgrade.
Watch the 3 minute video, I'd like to start going through all the different game ideas to filter out what might work for our teams, and try some out here and there at our meetings.
OPS would be a great opportunity for this, since we are starting from scratch.
This is was a cool quote from a follow up video I watched from the books author
"You find things that you're not looking for, even when your not looking.
But if you're not looking for something, then you won't find anything"