Not sure why you're getting downvoted since it's completely true. Making a cross-browser game is hard. For regular apps it hardly matters but when you need to

Not sure why you're getting downvoted since it's completely true. Making a cross-browser game is hard. For regular apps it hardly matters but when you need to run complicated logic 60 times a second differences between browsers and even nuances in implementations between platforms (Windows vs Mac, desktop vs mobile) start to matter. And then we have all the rendering and sound caveats.