unity
選択的
accuracy
antique
circle
classic
close up
cog
cogwheel
concept
connection
cooperation
dirty
electric
energy
engine
equipment
factory
focus
gear
gray
greasy
grunge
industrial
industry
interlocked
invention
iron
machine part
machine teeth
manufacturing
mechanism
metal
motor
nobody
power
progress
reliability
retro
revival
shiny
steel
symbol
teamwork
technology
teeth
turn
up
wheel
working