Note this intentionally not accurate to represent an in progress app

• T Key: Resize browser window to fit mockup (broken in Chrome & untested)
• Space: Toggle visibility of Mockup
• Up Arrow: Increase mockup Opacity
• Down Arrow: Decrease mockup Opacity
• Right Arrow: Next mockup
• Left Arrow: Previous mockup
• Mouse Drag: Drag the image around to tweak positioning

More Info