This robot is based on a toy I have. The toy is made from card with a few plastic gears. You turn it on and it drives in a straight line until it hits a wall. The snowflake on top stays still and the lower half rotates until it can drive in a line again away from the wall (because the drive wheel is off centre and the snowflake on top is free to rotate. LDD and pdf version of construction available to download. The program is set medium motor to full speed and power until cancelled. The large wheel is the front when the robot moves forward. This is a C-model using only the parts from 31313 Mindstorms EV3.