Wheel = Zoom, MMB = Pan, RMB = Orbit
LMB = Draw Path
Enter = Finish Path
Connect to Start = Finish Path
Shift+LMB on Path = Delete Path
LMB on Path = Add Point
Shift+LMB on Point = Delete Point
LMB+Drag on Point = Move Point
LMB = Paint Mask, Shift+LMB = Erase Mask