Very promising start! The amount of customization options is very neat, and the nightmare sequence had a great atmosphere! Plus I love the neat things you're doing with the selectable text in the demo and how the words will change or the sound effects trigger. Fun!
I'd definitely recommend enlisting the help of a beta reader. I definitely noticed a few typos and they'll also be able to help out when the coding decides to be a butt and not give the right pronoun or give the right form of the pronoun.
I'm very interested in this and looking forward to its development!