Objective: Go through multiple revisions of a project to improve it.
Assignment: Build a car to climb as steep a slope as possible. There is a board in the lounge you can lean up against the wall at different angles. As your vehicle climbs the board, increase the angle until the vehicle is no longer making progress.
Figure out what is holding the vehicle back (not enough friction? motor stalling out? vehicle tipping over? or something else...) and improve the vehicle somehow.
For a further challenge...: