Thanks for thorough review!
Gifts are just collectables. 4 of them make a frame and the last one (from room (2.5) adds a heart. After finishing the game this collectables "remake" boring white square core into famous Cube Companion from Portal series. So, it is like skin customization :D
I am thinking of adding more mechanics to broaden spectrum of pickups and add more inсentives to explore, because nobody wants to loot skins instead of powerups :)
Thanks again, I hope to shock you with updates later!