"Wisdom was not at the top of the graduate school mountain, but there in the sandbox..." Robert Fulgham.
Beautiful, ocean washed sand with log and stone retainer walls.
Sandbox running water flows up through a large black locust tree slice and cascades down site excavated stone slabs.
Multi axis swings, or single rope swings such as tire swings and net seat swings are enormously fun. However, they require a large clearance space between supporting or other structures, up to 20' for an 8' tall swing.
All my swings are age appropriate fun, and not undersized (!), as are many commercially produced sets. I make them with high quality rope and chain, and where requested, with soft and lightweight, hand crafted, white cedar seats. Minimal impact on tree health is emphasized.
With completely natural woodland timbers, I build school playgrounds to National Playground Safety Code requirements. Residential projects follow these standards.
Beauty is as important as intelligent engineering and safety.
See article on tree house project:
https://www.townvibe.com/Ridgefield/July-August-2015/On-Top-Of-the-World/