Make a dark den.
Can you find a place in your house (or can you make a place in your house) where it is completely dark? What happens if you sit there? Do your eyes adjust to the dark?
What would you need in order to see?
Get someone to write a number on a piece of paper and give it to you in the dark. How will you be able to see the number.
I have written the answers below (don't cheat!).