An apparatus including a memory storing instructions and a control unit executing the instructions is provided. The control unit is configured to send signals to display first and second indicators on a display device. The control unit is further configured to receive first and second user inputs and, in response to the received inputs, to send signals to change a display state of the first indicator according to the first input. The control unit is further configured to send signals to change a display state of the second indicator according to the second input and initiate an operation to be performed based on a combination of the first and second inputs.