The UWell Caliburn GK2 has lights built into its glass screen that flash depending on your activity. These bars will activate to let you know when: The voltage for your device is low: the lights will blink red 10 times and the device will vibrate 3 times. The circuit for your device is open: the lights will blink blue 3 times and the device will vibrate 2 times. You vape for more than 8 seconds at a time (overtime): the lights will blink green 5 times and the device will vibrate 2 times. The device short circuits: the lights will blink yellow 4 times and the device will vibrate 4 times. The flashing lights on the device also change colour to indicate different power levels: Red: battery under 30% Blue: battery at 30-60% Green: battery over 60% When the Caliburn GK2 is finished charging, the device will vibrate once and the green light will remain steady.