I went from knowing nothing about Phaser to a working game in about two weeks for a game jam earlier this year. Really enjoyed working with it.

http://www.lmnopc.com/air-sea-golf/

The jam was "genre shift", where participants were supposed to take an existing game and shift it to another genre. I chose the Atari 2600 classic Air Sea Battle and turned it into a simple golfing game.

I liked the idea of using the 2600 as a starting point so I could worry less about the graphics and more about the physics and gameplay.

It's simple but it works. It's almost much more fun on a phone - the touch screen is more fun than a mouse for this one. :)