There is a design guideline for app icons??!!

https://plus.google.com/u/0/photos?pid=5965775208592653426&oid=116332965948849200590

As you can see the pic on the above, those apps (FIFA, Flipboard, Pocket, Umano, etc...) have the similar icon design. I have no idea why Android does not force all the app developer to make their app icons look like this. Doesn't it look much better?