How do I annoy my neighbors very discreetly?

I have these neighbors they don't like us for some reason. they leave all their lights on around their house at night. they also leave their balcony light on. they know it shines directly into our bedroom. I can't sleep so I put blankets up on the window. how do I get back at them very discreetly? they have been doing this for months now. I can't stand it! help please!
How do I annoy my neighbors very discreetly?
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