When a beloved pet goes blind, it doesn’t mean they can’t or don’t want to play fetch anymore, only that the game must change a bit. Lucy doesn’t care for commercial toys that chime constantly, especially once she’s got it in her mouth. When the toy is thrown up in the air, the accelerometer determines that it’s in free fall and triggers an interrupt on the PIC. The piezo buzzer starts beeping so Lucy can find it, then stops a short while later and waits for the next free fall. We bet that communication between [Bud] and Lucy is already pretty good, but maybe she could be more expressive with a doggy soundboard.