Using *-mask-alpha.png files for cleaner die-cut boundaries
body-mask-alpha.png
left-arm-mask-alpha.png
right-arm-mask-alpha.png
tread-mask-alpha.png
tread-mask-alpha.png (shared)
envelope-mask-alpha.pngbody-mask-alpha.png - Body shape maskleft-arm-mask-alpha.png - Left arm shape maskright-arm-mask-alpha.png - Right arm shape masktread-mask-alpha.png - Tread shape mask (used for both treads)envelope-mask-alpha.png - Envelope shape mask
Note: These *-mask-alpha.png files use alpha channel masking
for smoother edges compared to the *-diecut-mask.png files used in the
original parts test.