As I played I couldn't stop thinking about how you implemented the cutout sphere, I've seen similar effects with shaders that use the depth buffer, but it looks like you also cutout vertices from physics meshes or something like that too? That was a truly distractingly interesting problem that you solved seamlessly. The game idea is great, I love the idea of revealing a hidden world, and your implementation choice to have the sphere stuck in one spot made for fun challenging puzzles like jumping across the tree tops. Really glad I got to play this!
I'm glad you liked it! The sphere works by assigning a custom surface shader material to all objects that will render the surface transparent if it is inside/outside the portal (and tint the color blue as it gets close to the edge). Making the collisions work was a pain, but basically I wrote my own player controller that will check if a collision point is inside/outside the bubble before having the player collide with it.