It started with some 2x6s attached to the wall and mango tree:

Some more 2x6s to check the dimensions:

Added joists and posts:

Added floorboards around the trunk, using a creative diagonal joist:

Added posts for the handrail and a slide:

Added the handrail and a protective netting:

The slide was too fast and ended on concrete, so I removed it. Then I secured the mesh with paracord:

Done