Drip is a simple drawing/painting application for OS X. The focus is on
drawing and as such, it makes a terrible image editor aside from simple
things like drawing mustasches on people (think Painter and not Photoshop).

At the moment it has support for layers, blend modes, recording/playback
(including playing back your drawings into a video) and undo/redo. There
is at the moment only one brush with a number of options and an eraser.

I've written it with the intention of adding network collaboration but
haven't written the code yet (check for Drop in the Mac App Store to see
my proof-of-concept). It certainly would make things simpler if I could
assume only one user.