//* left/right/on/off Menu Functionality optimized for LED for the Homework Problem *
#define MAX_LED (0b00001000)
#define MIN_LED (0b00000001)
static uint8_t LED_current = 1; // one hot addressing
static uint8_t LED_mode    = 0; // one bit per LED

...
if ( _key_off_pressed_detected_ ) {
   LED_mode = LED_mode & ~LED_current;
}
...
if ( _key_on_pressed_detected_ ) {
   LED_mode = LED_mode | LED_current;
}
...
if ( _key_left_pressed_detected_ ) {
    if ( LED_current<MAX_LED) {
        setLED( (getLED() & ~LED_current) | (LED_mode & LED_current) );
        LED_current = LED_current<<1;
        if ( 0 != (LED_mode & LED_current) ) {
            _set_coefficients_for_long_blink_
        } else {
            _set_coefficients_for_short_blink_
        }
    }
}
...
if ( _key_right_pressed_detected_ ) {\
    if ( LED_current>MIN_LED) {
        setLED( (getLED() & ~LED_current) | (LED_mode & LED_current) );
        LED_current = LED_current>>1;
        if ( 0 != (LED_mode & LED_current) ) {
            _set_coefficients_for_long_blink_
        } else {
            _set_coefficients_for_short_blink_
        }
    }
}
...


// do a blink inside the code for blinking (toggle, not on/off!)
setLED( (getLED() ^LED_current) );