It was weird! But in an enjoyable sort of way. My only major problem with it was that it was a bit hard to tell where I was in the typing, and once I made one mistake, the rest came quickly. I guess that's the price to pay... if you showed everything I typed, it would have made it too easy. Maybe some response for a correct answer, such as a typewriter keystroke sound, to let you know you had a correct hit, would have helped without making it too easy.
There was a problem with audio channels, when I got a mistake early on, and grandma laughed, the voiceover dialogue stopped. That straight ruined my chances on that playthrough. Besides that, interesting idea and creepy fun grandma graphics!