If you want a lesson in humility, try to make a contraption to open a door that has a regular round doorknob. In particular, opening a door that swings toward

If you want a lesson in humility, try to make a contraption to open a door that has a regular round doorknob. In particular, opening a door that swings toward the opener is a complicated dance of leverage and balance, not to mention the fiddly bits to actually rotate the knob. Interestingly, US ADA (disability act) requires commercial buildings to use handle-style doorknobs. The robot uprising would have a lot easier time getting through those.