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Thanks for your kind words. I'm working on a sequel for FoE but it's not nearly finished. I encourage you to start working on a similar game, it's fun to play with those mechanics and there is so much to explore. Here is another game you may like to try: https://geckoo1337.itch.io/project-a also there is Antichamber and soon (I hope) Magnifold Garden.
You got me curious so I looked at asset from Unity Store and there is quite some:
There is free ones like https://assetstore.unity.com/packages/tools/particles-effects/gater-portals-system-59185
This one seems really great (but not free) and can play on scale (spoiler for FoE episode 2 ...), and there is a demo only
https://assetstore.unity.com/packages/tools/particles-effects/portalkit-pro-vr-a...
Even if you don't use Unity, it can be great for learning. I saw video of Memory of a Broken Dimension but did not know it was out, I need to try it!