From Tekkotsu Wiki

• To run the robot: unplug the charger, then press the Power button. The power LED will flash red/green for a second, then turn steady green as the robot emits a single beep. It is now ready for Tekkotsu to control.
• The Play (Tekkotsu "green" button) and Advance (Tekkotsu "yellow" button) are for user inputs
• If the cliff detector is triggered, Tekkotsu will enter emergency stop mode

Indicators When Charger Is Plugged In

• Pulsing orange: battery is charging
• Steady green: battery is fully charged
• Green with sad four-note beep: Tekkotsu is trying to talk to the robot (must disconnect the charger to proceed)
• Very rapid red/green pulsing: Tekkotsu was running when the charger was plugged in; robot is now stopped

Indicators When Not Charging

Note: these are the default LED meanings. User programs can set the LEDs if they wish.

• No lights: robot is turned off
• Steady green: robot is powered up and ready to run
• Alternating red/yellow/green: emergency stop mode (click Un-Stop in ControllerGUI to resume)
• Steady yellow: battery running down
• Steady red: battery almost dead