This is an awful idea. Who wants a cat that dies every 12 hours?! This is super disturbing, upsetting and stressful. Absolutely terrible for those that care about cats. What if you happen to be too ill to get to your laptop in 12 hours? On a flight? In an accident? At work? Forgot your laptop? Forgot to check off tasks? All of this will kill the poor cat. If this was changed to the cat just being "sad" or "hungry" if you don't do your tasks, it would be better. Otherwise it encourages users to create "fake" tasks just to keep the cat alive.
