Gorgeous, gorgeous UI! Portal makes me want to upgrade my monitor, that's just how beautiful it is. The number of "portals" to look at feels a bit limited though, I wish there was more variety
I started using Portal because I wanted really immersive nature sounds. I've grown up camping, hiking, and being in nature, and I wanted to be able to bring some of that to my everyday life. Portal delivers. Its sounds are high quality, and I use them when I working and when I need to de-stress. I don't use the sleep feature, but I think it makes sense. The UI is a little atypical, but the app is still easy to use, and it feels special. Money well spent.
