As an intern at PayPal, a designer asked me if I could build a prototype of a new cart screen he designed.
With an initial version of the opening and closing animation built in just 15 minutes, the version shown below took around two days to complete in full, and allowed us to conduct detailed on-device user tests, validating some choices and finding issues with others.
Built in Quartz Composer using Origami, the final version uses several hundred patches, and properly shows cart contents and totals with tax, without requiring that users follow a set script.