Unify the "Play" and "Stop" buttons and just toggle the icon between them based on current state

It's nice to be able to play and pause quickly without having to look at the buttons and move the mouse back and forth. If you unify the play and stop buttons (since they're mutually exclusive anyway) you can just rest your mouse on it and click once to pause and again to unpause, without the need to move the mouse or look at it.