This Phaser plugin helps make your game responsive and free of black bars.
This is a new plugin by Hristiyan Dodov that attempts to solve the perennial problem of making your game responsive:
"You provide flexcale with a minWidth and minHeight values. They represent your desired game resolution. If the browser window is smaller or larger, flexcale dispatches a signal with a scale value that your game content must have in order to fit.
You can optionally provide a maxWidth and maxHeight values. With them, you can set a maximum size of the game, in case you don't want it to always be as big as its container.
A resolution option is also available. If you set that to 0.5, the game canvas will be half as big, but CSS transform with value scale(2) would be applied to it. This reduces the amount of pixels rendered while the game still fits the screen. It can drastically increase performance as well, so you can provide it as a setting in your game for players with slower devices."