I used the Sketch "Delicious" free UI Kit for a food recipes app. It includes 11 pixel-perfect screens. I just added Proto.io interactions and created a great prototype! This Delicious UI Kit was designed by Robert Anitei Sketch source: https://www.sketchappsources.com/free-source/1765-delicious-ui-kit-sketch-freebie-resource.html

Game Title Screen Project. Using a minimal design with overlay transitions, mouse hover effects and states.

A Simple recreation of the Messenger bubble using Proto.io stock images. Basic functions such as drag/drop to screen corners, drag to the bottom to delete, swipe down to reveal 'contents hidden' to bring the bubble back to the screen and tap bubble to show conversation.