To change the shape, size, animation and other details of your play button then navigate to Theme >> Play Button:

(Please note that if you want to change the colors of the play button then please check this article on Player Colors.)

There are additional options here to further customize the look of your player by clicking on the Play Button option. You'll see this:

Button Animation - Choose from a variety of animations for your play button

Button Size - Change shape of entire play button including the background

Button Shape - Choose from a variety of shapes for your play button

Button Border - This will add a border around your play button and background. The color of this is controlled by the Player Bar color described above.

Preview Duration - This will show the duration of your video right underneath the play button

Play Button Image - Here you can add a URL for your own play button, or upload it by dragging it and dropping it into the supplied field

Button Position - Choose from a variety of positions for your play button to appear on your video