Built a treehouse with my boys this summer

Spent the last 6 weekends turning an old oak in our backyard into something actually functional. Started with just some rope and a platform idea, ended up with walls, a roof, and a pulley system to haul stuff up. My 7 year old did more supervising than helping but my 10 year old was right there with me learning to measure twice. Best parenting moments I've had in years. Total cost maybe 300 bucks in lumber.