+ (p [the caster will go at the back of the robot and provide a third
+ point of contact for the robot, making it easier for it to
+ balance.])
+ (figure
+ :legend "caster"
+ (video :file "4-caster-to-deck.ogv"))
+ (p [check])
+ (enumerate
+ (item [what would happen if the robot did not have a caster?])))
+ (section
+ :title [wheels]
+ (p [now we will attach the wheels.
+ this makes the motor movement transform into robot movement!])
+ (figure
+ :legend "wheel"
+ (video :file "5-wheel-to-robot-assembly.ogv"))
+ (p [check])
+ (enumerate
+ (item [does the robot's wheels scrape the deck?])
+ (item [what would happen if the robot had no wheels?])
+ (item [what does the tread do?])
+ (item [what is the tread?])
+ (item [what kind of screw is used?])))