This train uses a colour sensor to detect yellow and red bricks to play train sound effects. The force sensor, acts like a touch sensor and, like the distance sensor, changes the direction of the motor.
Only one motor is used to make this train. The key is to get all four wheels as close together as possible. The smaller the distance between the wheels, the less likely it is to topple on the corners. Also.. don't make it too top-heavy!
You can use the built-in gyro sensor to play a sound when the train crashes (or "tilts").
