Adjust the distance knob to control how far back the arms are pulled before release and height knob to control how high up the Crossbow is aimed before firing. This construction kit challenges you to not only Build Genius but also build a fully functional VEX Robotics Crossbow at the same time! Explore the technology behind some of the most influential inventions of our culture's Age of Innovation! HEXBUG believes in using the fun of robotic toys to teach kids important STEM principles through hands-on learning. The VEX Robotics Crossbow features two alternate builds for more robotic fun! All Crossbow's construction pieces are compatible with educational VEX IQ pieces to create your own custom VEX robot and explore unlimited possibilities. Caution: Do not aim at eyes or face. To Avoid Injury: Use only projectiles designed for this product. Do not modify projectiles or projectile launcher.