Hi guys. We have recently got a design 'competition' where we build a vehicle that will propel itself 1.0 m forward and then fire a projectile in attempt to hit a target that is 2.0 m away, perpendicular to the direction of travel. The vehicle will be traveling on sand, and can only move by gravitational or elastic energy, meaning no motors or batteries. We can choose our own mass. Right now, I just want to know some possible ideas and materials to use, because I'm having trouble even starting the assignment. It would be awesome if we can discuss about some ideas, even the faintest ones, and hopefully through them, I can get this project started. Just comments/suggestions etc will be much appreciated! I don't want any answers or anything, just to hear some of your opinions. Thank you!