We designed the electronics to be simple and flexible, because we had not finalized the robot design when we started and planned to try a variety of control algorithms, actuators, and communications methods. We also needed the electronics to be small and light. We decided to go with fairly small SMT parts for the final design, and were able to get a microcontroller, 10 status LED's, 4 FET's for driving actuators, and the programming/power header onto the 25mm x 25mm board, plus connection points for 4 actuators and 4 sensors. We tried making the board even smaller, but it became too hard to assemble. Our strategy for simple and flexible worked out - we've since used leftover boards for 3 other, totally unrelated projects.