After the traumatic event at the window, when you see your parents disappear, you’re supposed to jump through that same window. That takes you outside the house, and from there the rest of the world opens up for you to explore.
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Thank you for the description. I played again and managed to complete the game and save Christmas! You've done well drawing everything and creating a whole world.
I think part of the issue is sometimes things looked like impassable walls to me for some reason and I didn't realise I could walk through them, but I did eventually find I could go through something to find the window up the top and then I was away, so thanks for the help figuring that out! Great job!