Kamina had never heard of written language until he came to the surface, and with all the giant robots to fight, hadn't bothered to learn to read since he got there. So, the first time he heard of Cayce's cultural festival was from her speech. He ran to the nearest planter and grabbed some dirt, which he spread on the ground to represent dirt. He drew his flag (http://randomc.animeblogger.net/image/Gurren%20Lagann/Gurren%20Lagann%20-%2023%20-%20Large%2035.jpg) on a piece of paper. He also drew a picture of his ganmen, Gurren Lagann beating up some beastmen. "All I need is some mole-pigs..." Kamina mumbled.