Graphical user interface element

A system comprising:

• one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising:
• presenting a user interface on a user device, the user interface including a graphical user interface element, the graphical user interface element including a base layer and a top layer, wherein a presentation width of the top layer is initially set to zero;
• determining a user interaction with the graphical user interface element;
• and
• in response to the user interaction, dynamically expanding the presentation width of the top layer such that the top layer overlays the base layer as the width increases.

One or more computer-readable storage media encoded with instructions that, when executed by one or more computers, cause the one or more computers to perform operations comprising:

• presenting a user interface on a user device, the user interface including a graphical user interface element, the graphical user interface element including a base layer and a top layer, wherein a presentation width of the top layer is initially set to zero;
• determining a user interaction with the graphical user interface element;
• and
• in response to the user interaction, dynamically expanding the presentation width of the top layer such that the top layer overlays the base layer as the width increases.