Hey I really like the concept! Fits the theme! I may have been slightly confused how to play though... I tried going to the yellow portal thing but it didn't do anything. I tried pressing E there as well. Was there something else I needed to do? At some points I didn't see any doors so it seemed like nothing was crumbling. Maybe it just was glitching out for me? Was I supposed to plant the tree in a certain spot? Anyway seems pretty cool! I can definitely see how a lot could be done with the idea. Good work!!
When you go to the past, you are able to change things that later influence the level in the present and help you finish it. But you can’t finish the level in the past, so in order to go through the yellow portal, you need to be back in the present again.
And about the trees: You can place them at different spots, but you don’t need to do that in order to finish the game as we haven’t fully implemented the obstacle you were supposed to block with the trees.