nice work in my favourite chamber style. i did a video but it is nearly 13 mins and i don't think that's worth uploading
as it contains a lot of failed jumping attempts..
maybe you can give me feedback if this was an unintended solution:
after deactivating the grids from the room on the first floor and managed jumping on the second floor with the funnel button i did a portal in the first room where i started, throwing the cube again through this portal on the funnel button. then i went back to room 1 shooting a portal beside the exit. i went through this portal , shooting another portal to the opposite of the funnel, landing on the spot with the cube. then i jumped from the cube to the funnel, headed to the exit, respawned the cube sending it through the funnel activating the exit door ... the only bug i found was one time when the grids on the first floor were off even when there was no cube at the button.
Outstanding decayed map and a great puzzle. Well done, thanks for creating.
Simply cool! 5/5
Loved the puzzle...great mapping, too...