That's when it's between the line of "You have to buy the hardware" and "Emulate it". Something too old for modern devices, and too new for emulators to have been made.

I still want to fucking play the original Infinity Blade. I WAS SO JEALOUS of my brother because he had his fancy Iphone 4 and could play. But by the time I got a phone it was already old news and taken off the app store.